Cylindrical lithium secondary battery

Abstract

This invention provides a lithium secondary battery, comprising: a battery casing; an electrode assembly housed within the battery casing; and an electrolyte, wherein the electrode assembly includes a positive electrode comprising a positive electrode active material, a separator, and a negative electrode comprising a negative electrode active material, and the electrolyte comprises LiPF6 as a lithium salt and ethylene carbonate as an organic solvent, wherein the ratio of the diameter (r) to the height (h) of the battery casing of the lithium secondary battery (shape factor ratio) is 0.4 or more, and satisfies the condition of mathematical formula (1), wherein in mathematical formula (1), h is the height (mm) of the battery casing, r is the diameter (mm) of the battery casing, and W LiPF6 The amount of LiPF6 relative to the total weight of the electrolyte, expressed as a percentage (%), W EC It is the amount of ethylene carbonate relative to the total weight of the electrolyte, expressed as a percentage (%), and W EL This represents the total weight (g) of the electrolyte contained in the lithium secondary battery. [Mathematical formula (1)]

Description

Technical Field

[0001] This invention relates to a lithium secondary battery, and more specifically, to a cylindrical lithium secondary battery with improved high-temperature durability and long-term life characteristics.

[0002] Cross-references to related applications

[0003] This application claims priority to Korean Patent Application No. 10-2023-0093983, filed on July 19, 2023, and Korean Patent Application No. 10-2024-0095334, filed on July 18, 2024, the disclosures of which are incorporated herein by reference. Background Technology

[0004] With the technological advancements in electric vehicles and portable electronic devices, the demand for lithium-ion batteries as an energy source has increased significantly.

[0005] Based on the shape of the battery casing, lithium secondary batteries can be classified into cylindrical, prismatic, and pouch batteries. In a cylindrical battery casing, a jelly-roll-shaped electrode assembly, prepared by sequentially stacking sheet-like positive electrodes, a separator, and a negative electrode and then winding them in one direction, is housed within the casing. A cover plate is then used to cover the top of the casing, thus forming a sealed cylindrical battery. The positive and negative electrodes are respectively provided with strip-shaped positive and negative electrode tabs, which are connected to electrode terminals for electrical connection to an external power source. For reference, the positive terminal is the cover plate, and the negative terminal is the battery casing. However, for conventional cylindrical batteries with this structure, the current is concentrated on the strip-shaped electrode tabs, resulting in high resistance, significant heat generation, and poor current collection efficiency.

[0006] However, for small cylindrical secondary batteries with a form factor of 18650 (18mm in diameter × 65mm in height) or a form factor of 21700 (21mm in diameter × 70mm in height) that were mainly used in the past, resistance and heat generation were not major issues.

[0007] However, in recent years, with the increasing need for electric vehicles to have longer driving ranges and faster charging rates, there is a growing consideration to develop and use large cylindrical secondary batteries with larger form factors, such as 46800 (a cylindrical secondary battery with a diameter of 46 mm and a height of 80 mm). Furthermore, to improve the fast-charging characteristics of such large cylindrical secondary batteries, a so-called tabless cylindrical secondary battery has been proposed, in which the current collector itself, representing the uncoated portions of the positive and negative electrodes, is used instead of separate strip-shaped electrode tabs.

[0008] Large cylindrical secondary batteries with tabless structures not only exhibit relatively large capacity characteristics and energy density, but also have the advantages of improving the production efficiency and reducing the unit cost of cylindrical secondary batteries for electric vehicles. Furthermore, because the tabless structure increases the electrical connection (contact) area between the electrode tabs and terminals while reducing the number of components and shortening the electron travel distance, output characteristics are improved, and heat generated during charging and discharging can be dissipated.

[0009] However, for large cylindrical secondary batteries using tabless structures, a pressing process is performed on the uncoated active material layer in order to provide sufficient weldability to the casing and terminal parts. As a result, the electrolyte cannot move normally because the electrolyte movement path between the positive electrode, separator and negative electrode in the wound electrode assembly is blocked, thus resulting in a problem of reduced electrolyte wettability.

[0010] Therefore, there is an urgent need to develop a technology that can improve the overall performance of large cylindrical secondary batteries suitable for medium and large-sized devices such as automobiles by improving the wettability of the electrolyte. Summary of the Invention

[0011] Technical issues

[0012] One aspect of the present invention relates to a lithium secondary battery in which the composition and amount of electrolyte can be adjusted according to the size of a large lithium secondary battery using a tabless structure to establish optimal electrolyte wetting conditions, thereby achieving excellent high-temperature durability and cycle characteristics.

[0013] Technical solution

[0014] According to one embodiment, the present invention provides a lithium secondary battery, comprising: a battery casing; an electrode assembly housed within the battery casing; and an electrolyte.

[0015] The electrode assembly includes a positive electrode containing a positive active material, a separator, and a negative electrode containing a negative active material.

[0016] The electrolyte comprises LiPF6 as a lithium salt and ethylene carbonate as an organic solvent.

[0017] Wherein, the ratio of the diameter (r) to the height (h) of the battery casing of the lithium secondary battery (shape factor ratio) is 0.4 or more, and satisfies the condition of mathematical formula (1):

[0018] [Mathematical expression (1)]

[0019]

[0020] (In mathematical formula (1), h is the height of the battery casing (mm),

[0021] r is the diameter (mm) of the battery casing.

[0022] W LiPF6 The amount of LiPF6 is expressed as a percentage (%) relative to the total weight of the electrolyte.

[0023] W EC It is the amount of ethylene carbonate relative to the total weight of the electrolyte, expressed as a percentage (%).

[0024] W EL This indicates the total weight (g) of the electrolyte contained in the lithium secondary battery.

[0025] The lithium secondary battery includes uncoated portions on at least a portion of the positive electrode and the negative electrode where no active material layer is formed, and may be a battery with a tabless structure, wherein the uncoated portion of the positive electrode or the uncoated portion of the negative electrode is defined as an electrode tab.

[0026] The positive electrode active material is a lithium transition metal oxide containing nickel (Ni) and cobalt (Co), wherein the lithium transition metal oxide satisfies mathematical formula (2).

[0027] Mathematical expression (2):

[0028] 18≤X Ni / X Co ≤48

[0029] (In mathematical expression (2), X) Ni X is the molar percentage of Ni in all metals other than lithium in lithium transition metal oxides. Co It is the molar percentage of Co in all metals other than lithium in lithium transition metal oxides.

[0030] Beneficial effects

[0031] As in the lithium secondary battery of the present invention, when the composition and amount of the electrolyte meet specific conditions according to the size of the battery cell and the composition ratio of nickel (Ni) to cobalt (Co) in the positive electrode active material meets specific conditions, excellent high-temperature durability and cycle characteristics can be achieved because optimal electrolyte wetting conditions can be established and side reactions at the interface between the positive electrode and the electrolyte can be minimized. Attached Figure Description

[0032] Figure 1 This is a diagram showing the stacked state of the electrode assembly of the present invention before winding.

[0033] Figure 2 This is a cross-sectional view showing the structure of the electrode plate of the electrode assembly according to an embodiment of the present invention.

[0034] Figure 3 This is a diagram illustrating the structure of an electrode assembly for illustrating an example of the present invention.

[0035] Figure 4 This is a cross-sectional view showing the structure of a cylindrical battery with a tabless structure according to an embodiment of the present invention.

[0036] Figure 5 This is a cross-sectional view showing the structure of a cylindrical battery with a tabless structure according to another embodiment of the present invention.

[0037] Figure 6 This is a diagram illustrating the battery pack of the present invention. Detailed Implementation

[0038] It will be understood that the words or terms used in the specification and claims should not be interpreted as having the meaning defined in a common dictionary, and it will be further understood that, based on the principle that the inventors may appropriately define the meaning of words or terms to best interpret the invention, the words or terms should be interpreted as having a meaning consistent with their meaning in the context of the related art and in the technical concept of the invention.

[0039] For conventional large cylindrical lithium-ion batteries using tabless structures, the lower electrolyte wettability compared to smaller batteries makes it difficult to achieve the desired performance with the same chemical properties as smaller batteries. Specifically, when increasing the amount of electrolyte injected into the limited internal space of the cylindrical cell during the fabrication of large cylindrical secondary batteries, the internal pressure increases as the internal free space decreases. As a result, since gaseous byproducts generated during formation do not escape to the outside of the electrode assembly but remain continuously inside, the electrolyte is squeezed out of the electrode assembly, reducing wettability. Conversely, if the internal free space increases due to a decrease in the amount of electrolyte injected, the wettability remains low because the electrolyte is difficult to absorb into the electrode assembly. As mentioned above, electrolyte wettability is closely related to cell resistance. That is, if the electrolyte is insufficient or wettability is reduced, the resistance increases (Seong Jin An et al 2017 J. Electrochem. Soc. 2017, 164A1195).

[0040] Therefore, the inventors conducted extensive research on improving the performance of large cylindrical secondary batteries and found that, with the injection of an appropriate amount of electrolyte, proper wettability can be ensured to suppress the increase in the initial resistance of the cell and improve the fast charging cycle characteristics. For this purpose, a method for calculating the appropriate amount of electrolyte injection was discovered, thus completing the present invention.

[0041] The lithium secondary battery of the present invention will be described in detail below.

[0042] Specifically, the present invention provides a lithium secondary battery, comprising: a battery casing; an electrode assembly housed within the battery casing; and an electrolyte.

[0043] The electrode assembly includes a positive electrode containing a positive active material, a separator, and a negative electrode containing a negative active material.

[0044] The electrolyte comprises LiPF6 as a lithium salt and ethylene carbonate as an organic solvent.

[0045] Wherein, the ratio of the diameter (r) to the height (h) of the battery casing of the lithium secondary battery (shape factor ratio) is 0.4 or more, and satisfies the following mathematical formula (1):

[0046] [Mathematical expression (1)]

[0047]

[0048] (In mathematical formula (1), h is the height of the battery casing (mm),

[0049] r is the diameter (mm) of the battery casing.

[0050] W LiPF6 The amount of LiPF6 is expressed as a percentage (%) relative to the total weight of the electrolyte.

[0051] W EC It is the amount of ethylene carbonate relative to the total weight of the electrolyte, expressed as a percentage (%).

[0052] W EL This indicates the total weight (g) of the electrolyte contained in the lithium secondary battery.

[0053] Preferably, in mathematical formula (1), It can be in the range of 5.65 to 8.6, and more preferably in the range of 6.5 to 8.6.

[0054] exist When the value meets the above range, the performance of the secondary battery can be effectively improved because the optimal electrolyte wetting conditions can be established according to the size of the battery cell.

[0055] The lithium secondary battery of the present invention can be a cylindrical lithium secondary battery with a shape factor ratio of 0.4 or more, preferably 0.4 to 0.6.

[0056] In mathematical formula (1), W ELW is the total amount (g) of electrolyte actually injected into the battery casing, which can vary depending on the size and dimensions of the battery cell. Specifically, for cylindrical lithium-ion secondary batteries with a shape factor ratio of 0.4 to 0.6, W... EL The preferred amount is about 30g to 50g.

[0057] Preferably, for cylindrical batteries with a shape factor ratio of 0.4 to 0.5, W EL It can be in the range of approximately 35g to 50g. Furthermore, when the shape factor ratio is greater than 0.5 and less than or equal to 0.6, W EL It can be in the range of approximately 30g to 40g. If the amount of electrolyte injected into the battery casing (g) (W) EL If the amount of electrolyte injected into the battery casing is slightly smaller, the desired battery performance will be difficult to achieve due to reduced electrolyte wettability, and if the amount of electrolyte injected into the battery casing (g)(W) is slightly smaller, the desired battery performance will be difficult to achieve. EL If the concentration is slightly higher, gas production will increase, which could lead to explosions and electrolyte leaks.

[0058] In mathematical formula (1), W LiPF6 It is the amount of LiPF6 relative to the total weight of the electrolyte during electrolyte preparation, expressed as a percentage (%), wherein the viscosity of the electrolyte can be adjusted according to the amount of LiPF6.

[0059] Specifically, when preparing an electrolyte suitable for cylindrical lithium secondary batteries with a shape factor ratio of 0.4 to 0.6, W LiPF6 For example, it can be in the range of about 12% to 16% by weight, preferably 13% to 16% by weight. If W LiPF6 A slightly lower W value results in high fluidity due to the electrolyte's low viscosity, making it easier to inject into high-capacity batteries. However, this may reduce lithium-ion conductivity, leading to deteriorated cycle characteristics. Conversely, if W... LiPF6 A slightly larger value will result in decreased fluidity as the electrolyte viscosity increases, thus deteriorating the wettability of the electrolyte and reducing the achievement of initial performance. This may lead to a decrease in high-temperature durability and cycling characteristics.

[0060] In mathematical formula (1), W EC It is the amount of ethylene carbonate relative to the total weight of the electrolyte during electrolyte preparation, expressed as a percentage (%), wherein the viscosity of the electrolyte can be adjusted according to the content of ethylene carbonate.

[0061] Ethyl carbonate is an organic solvent with excellent affinity for carbon materials, and it is primarily used as a solvent for the electrolyte in lithium-ion secondary batteries. However, when the electrolyte contains even a slightly high amount of ethylene carbonate, the decomposition of ethylene carbonate during charging and discharging can generate a large amount of CO2 gas, which may adversely affect the performance of the secondary battery. Furthermore, ethylene carbonate is a high-melting-point solvent; if its content is slightly high, it can lead to deterioration of high-output characteristics and increased electrolyte viscosity due to reduced low-temperature properties and lower conductivity. Conversely, if the electrolyte contains even a slightly low amount of ethylene carbonate, the thermal stability and battery life may be reduced due to potentially decreased conductivity.

[0062] When the shape factor of the lithium secondary battery of the present invention is in the range of 0.4 to 0.6, it is desirable that the amount of ethylene carbonate in the electrolyte (W) is low. EC It ranges from about 13% to 25% by weight, preferably from 15% to 20% by weight. In W EC When the value meets the above range, the optimal electrolyte wetting conditions for a large-capacity cylindrical secondary battery can be established.

[0063] The high-temperature durability and cycle characteristics of lithium-ion batteries are closely related to the viscosity of the electrolyte. Specifically, when a high-viscosity electrolyte is injected into a large-capacity cylindrical lithium-ion battery with a shape factor ratio of 0.4 or higher, preferably 0.4 to 0.6, as described above, the reduced wettability of the electrode components leads to a significant decrease in the charging and discharging performance of the lithium-ion battery, or even an inability to charge and discharge. Conversely, when a low-viscosity electrolyte is injected into a large-capacity battery, the wettability of the electrode components is improved, but the charging and discharging performance of the lithium-ion battery is significantly reduced due to the low lithium salt concentration in the electrolyte.

[0064] In this invention, since the composition and amount of the electrolyte satisfy specific conditions such as the above-mentioned mathematical formula (1) according to the size of the battery cell, the optimal electrolyte wetting conditions suitable for large-capacity cylindrical lithium secondary batteries can be established, thereby enabling the preparation of lithium secondary batteries that exhibit excellent high-temperature durability and cycle characteristics. That is, since the wettability of the electrode components in the electrolyte can be improved while controlling the internal pressure of the cell by injecting an appropriate amount of electrolyte containing the optimal lithium salt (LiPF6) and ethylene carbonate (EC) into the limited internal space of the cylindrical cell, the increase in resistance can be suppressed and the high-temperature cycle characteristics can be significantly improved.

[0065] exist Figure 1 The diagram shows the stacked structure of the electrode assembly of the present invention before winding. Figure 2 The cross-sectional structure of the electrode plate (positive or negative electrode) of the present invention is shown in the figure, and... Figure 3 The structure of an electrode assembly according to an example of the present invention is shown. Furthermore, in Figure 4 and 5 A cross-sectional view of a cylindrical battery with a tabless structure according to an embodiment of the present invention is shown. Hereinafter, each construction of the cylindrical battery with a tabless structure according to the present invention will be described in more detail with reference to the accompanying drawings.

[0066] [Electrode Assembly]

[0067] Reference Figure 1 and 2 The electrode assembly A of the present invention can be prepared by winding a stack formed by stacking the diaphragm 12, the positive electrode 10, the diaphragm 12 and the negative electrode 11 in sequence at least once along one direction X.

[0068] In this case, the positive electrode 10 and the negative electrode 11 each have a structure in which an active material layer 21 is formed on the elongated sheet-like current collector 20, and may include an uncoated portion 22 in a portion of the current collector 20 in which the active material layer 21 is not formed.

[0069] If the positive electrode 10 and negative electrode 11, including the uncoated portion 22 as described above, are used, a battery with a tabless structure that does not include separate electrode tabs and at least a portion of the uncoated portion of the positive electrode 10 and negative electrode 11 defines the electrode tabs can be realized.

[0070] Specifically, the uncoated portion 22 can be formed longer along the winding direction X on one end of the current collector 20, and the battery with a tabless structure can be realized by connecting the current collector to the uncoated portion of the positive electrode and the uncoated portion of the negative electrode respectively and connecting the current collector to the electrode terminals.

[0071] For example, a battery with a tabless structure can be fabricated using the following method. First, a separator, a positive electrode, another separator, and a negative electrode are stacked sequentially, such that the uncoated portions 22 of the positive electrode 10 and the negative electrode 11 are positioned in opposite directions. Then, the electrodes are wound in one direction to fabricate a jelly-roll-type electrode assembly. Next, after bending the uncoated portions 22 of the positive and negative electrodes towards the winding center C, current collectors are welded and bonded to the uncoated portions of the positive and negative electrodes, respectively, and the current collectors are connected to the electrode terminals, thereby fabricating a battery with a tabless structure. Since the current collector has a larger cross-sectional area than the strip-shaped electrode tabs, and the resistance is inversely proportional to the cross-sectional area of ​​the current flow path, the cell resistance can be significantly reduced when a secondary battery is formed with the above structure.

[0072] The uncoated portions of the positive and negative electrodes can be processed into multiple independently bendable segments, and at least a portion of the multiple segments can be bent toward the winding center C of the electrode assembly.

[0073] The sections can be formed by processing the current collectors of the positive and negative electrodes using metal foil cutting processes such as laser cutting, ultrasonic cutting, and punching.

[0074] When the uncoated portions of the positive and negative electrodes are processed into multiple segments, deformation or damage to the uncoated portions can be prevented by reducing the stress applied to the uncoated portions during bending, and the welding characteristics with the manifold can be improved.

[0075] The current collector and the uncoated portion are typically joined by welding. To improve weldability, strong pressure must be applied to the weld area of ​​the uncoated portion to bend it as flat as possible. However, during this bending process, the shape of the uncoated portion may irregularly twist and deform, and the deformed portion may come into contact with electrodes of opposite polarity, leading to internal short circuits or microcracks in the uncoated portion. However, if the uncoated portions of the positive and negative electrodes are machined into multiple independently bendable segments, the stress applied to the uncoated portion during bending is reduced, thereby minimizing deformation and damage to the uncoated portion.

[0076] Furthermore, when the uncoated portion is processed into the segmented form described above, the multiple segments overlap during bending, thus increasing the weld strength of the current collector and preventing the problem of laser beams penetrating into the electrode assembly and ablating the diaphragm or active material when using modern technologies such as laser welding. Preferably, at least a portion of the multiple bent segments can overlap the upper and lower ends of the electrode assembly, and the current collector can be bonded to the overlapping multiple segments.

[0077] like Figure 3 As shown, the electrode assembly of the present invention can be configured such that an insulating layer 24 is additionally formed on the positive electrode 10. Specifically, the insulating layer 24 can be configured to cover a portion of the positive electrode active material layer and a portion of the uncoated portion along a direction parallel to the winding direction of the electrode assembly.

[0078] For a battery with a tabless structure (where the uncoated portion 22c of the positive electrode 10 and the uncoated portion 22a of the negative electrode 11 serve as electrode tabs), the electrode assembly is formed such that the positive electrode 10 protrudes above the separator 12 and the negative electrode 11 protrudes below the separator 12, and the protruding positive electrode 10 and / or negative electrode 11 are bent and then bonded to the current collector. When the positive electrode 10 or negative electrode 11 is bent as described above, the current collector of the positive electrode 10 or negative electrode 11 passes through the separator and is close to the electrode arrangement with opposite polarity, thus creating the possibility of positive and negative electrode electrical contact leading to an internal short circuit. However, as... Figure 3As shown, when an insulating layer 24 is formed that covers the positive electrode active material layer and a portion of the uncoated portion, the insulating layer 24 can prevent electrical contact between the positive electrode 10 and the negative electrode 11, thus preventing short circuits in the battery.

[0079] Preferably, the insulating layer 24 can be disposed on at least one side of the current collector of the positive electrode 10, and more preferably, it can be disposed on both sides of the positive electrode 10.

[0080] Furthermore, the insulating layer 24 can be formed in the region of the active material layer 21a of the positive electrode 10 that faces the negative electrode 11. For example, on the surface of the uncoated portion 22c of the positive electrode 10 facing the negative electrode 11 after bending, the insulating layer 24 can be formed by extending to the end of the uncoated portion 22c. However, for the surface opposite to the surface facing the negative electrode 11 after bending, it is desirable that the insulating layer 24 is formed only on a portion of the uncoated portion 22c, for example, before the bending point of the uncoated portion 22c. The reason for this is that if the insulating layer 24 is formed on the entire region of the uncoated portion on the surface opposite to the surface facing the negative electrode 11, it may not be able to function as an electrode tab because it cannot make electrical contact with the current collector.

[0081] The insulating layer 24 can be used as long as it can adhere to the positive electrode while ensuring insulation performance, and its material or composition is not particularly limited. For example, the insulating layer can be an insulating coating or an insulating tape, and the insulating coating can include organic adhesives and inorganic particles. In this case, the organic adhesive can be, for example, styrene-butadiene rubber (SBR), and the inorganic particles can be alumina, but are not limited thereto.

[0082] The diameter of the core of the electrode assembly of the present invention can be 5 mm or more, specifically 5 mm to 8 mm. When the diameter of the core of the electrode assembly meets the above range, the defect rate can be suppressed during the winding process for preparing the jelly roll electrode assembly, and sufficient space for electrolyte injection can be ensured in the cylindrical secondary battery. When the diameter of the core of the electrode assembly is less than 5 mm, problems such as venting may occur due to the increased internal pressure of the cell. Conversely, when the diameter of the core of the electrode assembly is greater than 8 mm, cell performance may deteriorate due to the reduced energy density per unit cell volume and reduced wettability of the electrolyte. In particular, for large cylindrical batteries with a form factor of 0.4 or more, cell performance can be improved because the electrolyte wettability of the electrode assembly can be improved by injecting an electrolyte with an appropriate viscosity level.

[0083] The total diameter of the electrode assembly can be a normal diameter corresponding to a large cylindrical battery with a shape factor of 0.4 or higher.

[0084] The following will describe each component of the electrode assembly of the present invention in more detail.

[0085] positive electrode

[0086] The positive electrode can be prepared by coating one or both sides of a long sheet-shaped positive electrode current collector with a positive electrode slurry, removing the solvent from the positive electrode slurry through a drying process, and then rolling it. A positive electrode including an uncoated portion can be prepared by leaving a portion of the positive electrode current collector uncoated during the coating process (e.g., one end of the positive electrode current collector).

[0087] As the positive electrode current collector, various positive electrode current collectors used in the art can be used. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, or silver can be used as the positive electrode current collector. The positive electrode current collector can typically have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to improve the adhesion of the positive electrode active material. The positive electrode current collector can be used in various shapes, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0088] In addition, the positive electrode slurry can be prepared by dispersing the positive electrode active material in a solvent (such as dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone or water).

[0089] As the above-mentioned positive electrode active material, commonly used positive electrode active materials in the art can be used, but preferably, lithium transition metal oxides containing nickel (Ni) and cobalt (Co) can be used. Specifically, the positive electrode active material may include lithium transition metal oxides that satisfy the following mathematical formula (2).

[0090] Mathematical expression (2):

[0091] 18≤X Ni / X Co ≤48

[0092] In mathematical expression (2), X Ni X is the molar percentage of Ni in all metals other than lithium in lithium transition metal oxides. Co It is the molar percentage of Co in all metals other than lithium in lithium transition metal oxides.

[0093] When the composition ratio of Ni to Co in the lithium transition metal oxide represented by Mathematical Formula (2) is less than 18, the interfacial resistance increases due to an increase in the side reaction with the electrolyte. On the contrary, when the composition ratio of Ni to Co satisfies the range of 18 to 48, the structural stability of the positive electrode active material is improved, thereby suppressing the oxidation reaction, and thus the side reaction with the electrolyte can be effectively prevented. Specifically, it is more desirable that the composition ratio of Ni to Co in the lithium transition metal oxide is 40 or less, or 35 or less.

[0094] Preferably, the lithium transition metal oxide can be represented by the following [Chemical Formula 1].

[0095] [Chemical Formula 1]

[0096] Li a Ni b Co c M 1 d M 2 e O2

[0097] In Chemical Formula 1, M 1 can be manganese (Mn), aluminum (Al), or a combination thereof, and can preferably be Mn or Mn and Al.

[0098] M 2 can be at least one selected from the group consisting of zirconium (Zr), tungsten (W), yttrium (Y), barium (Ba), calcium (Ca), titanium (Ti), magnesium (Mg), tantalum (Ta), and niobium (Nb), can preferably be at least one selected from the group consisting of Zr, Y, Mg, and Ti, and can more preferably be Zr, Y, or a combination thereof. M 2 The element is not necessarily included, but when included in an appropriate amount, it can play a role in promoting grain growth during sintering or improving the crystal structure stability.

[0099] a represents the molar ratio of lithium in the lithium nickel-based oxide, where a can satisfy 0.8 ≤ a ≤ 1.2, 0.85 ≤ a ≤ 1.15, or 0.9 ≤ a ≤ 1.2. When the molar ratio of lithium satisfies the above range, the crystal structure of the lithium nickel-based oxide can be formed stably.

[0100] b represents the molar ratio of nickel among all metals except lithium in the lithium nickel-based oxide, where b can satisfy 0.85 < b < 1, 0.87 ≤ b < 1, or 0.9 ≤ b < 1. When the molar ratio of nickel satisfies the above range, a high energy density can be exhibited to achieve a high capacity.

[0101] c represents the molar ratio of cobalt among all metals other than lithium in the lithium nickel-based oxide. Here, c can satisfy 0 < c < 0.06 or 0.01 ≤ c ≤ 0.05. When the molar ratio of cobalt satisfies the above range, good resistance characteristics and output characteristics can be achieved.

[0102] d represents the molar ratio of element M among all metals other than lithium in the lithium nickel-based oxide 1 , where d can satisfy 0 < d < 0.15, 0 < d < 0.14 or 0.01 ≤ d ≤ 0.12. When the molar ratio of element M 1 satisfies the above range, the structural stability of the positive electrode active material is excellent.

[0103] e represents the molar ratio of element M among all metals other than lithium in the lithium nickel-based oxide 2 , where e can satisfy 0 ≤ e ≤ 0.1 or 0 ≤ e ≤ 0.05.

[0104] Specifically, the positive electrode active material of the present invention can be Li(Ni 0.90 Mn 0.05 Co 0.05 )O2, Li(Ni 0.94 Co 0.04 Mn 0.02 )O2, Li(Ni 0.87 Mn 0.07 Co 0.04 Al 0.02 )O2 or Li(Ni 0.90 Mn 0.03 Co 0.05 Al 0.02 )O2.

[0105] The positive electrode paste may optionally further include at least one of a conductive agent and a binder.

[0106] The conductive agent is used to provide conductivity to the electrode. Among them, any conductive agent can be used without particular limitation as long as it has electronic conductivity and does not cause chemical changes in the battery. Specific examples of the conductive agent can be: 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 fiber, and carbon nanotube; powders or fibers of metals 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, and any one of them or a mixture of two or more of them can be used. Based on the total weight of the positive electrode active material layer, the content of the conductive agent can generally be 1% by weight to 30% by weight, preferably 1% by weight to 20% by weight, and more preferably 1% by weight to 10% by weight.

[0107] The adhesive enhances the adhesion between positive electrode active material particles and between the positive electrode active material and the positive electrode current collector. Specific examples of the adhesive include: fluoropolymer adhesives comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber adhesives comprising styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose adhesives comprising carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyol adhesives comprising polyvinyl alcohol; polyolefin adhesives comprising polyethylene or polypropylene; polyimide adhesives; polyester adhesives; and silane adhesives, and any one or a mixture of two or more of these can be used. Based on the total weight of the positive electrode active material layer, the adhesive content can be from 1% to 30% by weight, preferably from 1% to 20% by weight, more preferably from 1% to 10% by weight.

[0108] negative electrode

[0109] The negative electrode can be prepared by coating one or both sides of a long sheet-shaped negative electrode current collector with a negative electrode slurry, removing the solvent from the negative electrode slurry through a drying process, and then rolling it. A negative electrode including an uncoated portion can be prepared by leaving a portion of the negative electrode current collector uncoated during the coating process (e.g., one end of the negative electrode current collector).

[0110] As the negative electrode current collector, commonly used negative electrode current collectors in the art can be used, such as copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium or silver, and aluminum-cadmium alloys. The negative electrode current collector typically has a thickness from 3 μm to 500 μm, and similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to improve the adhesion of the negative electrode active material. The negative electrode current collector can be used in various shapes, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0111] In addition, negative electrode slurry can be prepared by dispersing the negative electrode active material in a solvent (such as dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone and water).

[0112] As a negative electrode active material, carbon-based negative electrode active materials used in the art can be used. Alternatively, silicon-based negative electrode active materials can be mixed with carbon-based negative electrode active materials and used as negative electrode active materials.

[0113] As the carbon-based active material, various carbon-based materials used in the art can be used. For example, graphite-based materials such as natural graphite, artificial graphite, and Kish graphite; pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and high-temperature sintered carbon such as coke derived from petroleum or coal tar pitch, soft carbon, and hard carbon. The shape of the carbon-based materials is not particularly limited, and materials of various shapes such as irregular, plate-like, flaky, spherical, or fibrous can be used.

[0114] In addition, the silicon-based negative electrode active material may include at least one selected from the group consisting of silicon (Si), silicon carbide (SiC), silicon chloride, silicon oxide (SiO x , where 0 < x < 2), and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si). The element Y may be selected from the group consisting of: Mg, Ca, strontium (Sr), Ba, radium (Ra), scandium (Sc), Y, Ti, Zr, hafnium (Hf), (Rf), vanadium (V), Nb, Ta, (Db), chromium (Cr), molybdenum (Mo), W, (Sg), technetium (Tc), rhenium (Re), (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), (Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B), Al, gallium (Ga), tin (Sn), indium (In), germanium (Ge), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and combinations thereof.

[0115] The carbon-based negative electrode active material and the silicon-based negative electrode active material may be included in a weight ratio of 99:1 to 95:5, and more specifically, may be included in a weight ratio of 95:5 to 97:3.

[0116] When the mixing ratio of the carbon-based negative electrode active material and the silicon-based negative electrode active material satisfies the above range, since the volume expansion of the silicon-based compound is suppressed and the capacity characteristics are improved, excellent cycle performance can be ensured. When the amount of the silicon (Si)-based compound is too small, it is difficult to increase the energy density, so it is difficult to increase the capacity of the battery. When the amount of the silicon (Si)-based compound is too large, the degree of volume expansion of the negative electrode may increase, so it is not desirable.

[0117] The negative electrode slurry may optionally further include at least one of a conductive agent and a binder.

[0118] A conductive agent is used to provide conductivity to the negative electrode. Any conductive agent can be used without particular limitation, as long as it has electronic conductivity without causing chemical changes in the battery. Specific examples of conductive agents can be: graphite, such as natural or artificial graphite; carbon materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermally cracked carbon black, carbon fibers, and carbon nanotubes; powders or fibers of metals 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, and any one or a mixture of two or more of these can be used. Based on the total weight of the negative electrode active material layer, the content of the conductive agent is typically from 1% to 30% by weight, preferably from 1% to 20% by weight, and more preferably from 1% to 10% by weight.

[0119] The adhesive improves the adhesion between particles of the negative electrode active material and the adhesion between the negative electrode active material and the negative electrode current collector. Specific examples of the adhesive can be: fluoropolymer adhesives including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber adhesives including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose adhesives including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyol adhesives including polyvinyl alcohol; polyolefin adhesives including polyethylene or polypropylene; polyimide adhesives; polyester adhesives; and silane adhesives, and any one or a mixture of two or more of these can be used. Based on the total weight of the negative electrode active material layer, the adhesive content can be from 1% to 30% by weight, preferably from 1% to 20% by weight, more preferably from 1% to 10% by weight.

[0120] diaphragm

[0121] The separator separates the negative and positive electrodes and provides a path for lithium ions to move. Any separator can be used without particular limitation, as long as it is typically used in lithium-ion secondary batteries. Specifically, porous polymer membranes can be used, such as those made from polyolefin polymers (e.g., ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers), or laminated structures having two or more layers. Alternatively, typical porous nonwoven fabrics can be used, such as nonwoven fabrics formed from high-melting-point glass fibers or polyethylene terephthalate fibers. Furthermore, coated separators incorporating ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength.

[0122] Cylindrical lithium secondary battery

[0123] Next, the cylindrical lithium secondary battery of the present invention will be described.

[0124] The cylindrical lithium secondary battery of the present invention includes: an electrode assembly formed by winding a positive electrode including an uncoated portion and a negative electrode including an uncoated portion; an electrolyte; a battery casing housing the electrode assembly and the electrolyte; and a sealing body sealing the opening end of the battery casing. Furthermore, a tabless structure can be implemented where at least a portion of the uncoated portion of the positive electrode or the uncoated portion of the negative electrode is defined as an electrode tab.

[0125] Preferably, the cylindrical lithium secondary battery of the present invention can be a large cylindrical battery with a shape factor ratio (defined as the value obtained by dividing the diameter of the cylindrical battery by its height, i.e., the ratio of diameter (T) to height (H)) of 0.4 or more, preferably 0.4 to 0.6. Here, the shape factor refers to the value representing the diameter and height of the cylindrical battery.

[0126] The cylindrical battery of the present invention may be, for example, a 46110 cell (diameter 46mm, height 110mm, form factor ratio 0.418), a 48110 cell (diameter 48mm, height 110mm, form factor ratio 0.436), a 4880 cell (diameter 48mm, height 80mm, form factor ratio 0.600), or a 4680 cell (diameter 46mm, height 80mm, form factor ratio 0.575). In the numbers representing the form factor, the first two digits represent the diameter of the cell, and the next two or three digits represent the height of the cell.

[0127] The cylindrical battery of the present invention is preferably a battery having a tabless-free structure that does not include electrode tabs, but is not limited thereto.

[0128] A battery with a tabless structure may have a structure in which the positive electrode and the negative electrode each include an uncoated portion on which no active material layer is formed, the uncoated portions of the positive electrode and the negative electrode are respectively disposed at the upper end and the lower end of the electrode assembly, the current collector is coupled to the uncoated portions of the positive electrode and the negative electrode respectively, and the current collector is connected to the electrode terminals.

[0129] exist Figure 4 and 5 A cross-sectional view of a cylindrical battery with a tabless structure according to an embodiment of the present invention is shown. In the following text, reference will be made to... Figure 4 and 5 A cylindrical battery according to an embodiment of the present invention is described. However, Figure 4 and 5 Only one embodiment of the present invention has been shown, and the structure of the cylindrical battery of the present invention is not limited to this. Figure 4 and 5 The scope of public disclosure.

[0130] The cylindrical battery 140 of the present invention includes a jelly roll-shaped electrode assembly 141 as described above, a battery housing 142 that houses the electrode assembly 141 and an electrolyte (not shown), and a sealing body 143 that seals the open end of the battery housing 142.

[0131] In this configuration, the positive and negative electrodes of the electrode assembly may each include an uncoated portion on which no active material layer is formed, and they may be stacked and wound such that the uncoated portions of the positive and negative electrodes are respectively located at the upper and lower ends of the electrode assembly. Since the electrode assembly has already been described above, only components other than the electrode assembly will be described below.

[0132] The battery housing 142 is a cylindrical container with an opening at the top, and it is formed of a conductive metal material such as aluminum or steel. The battery housing houses the electrode assembly 141 in the internal space through the opening at the top, and also houses the electrolyte (not shown).

[0133] Ideally, the cylindrical battery 140 of the present invention does not include a current interruption device (CID).

[0134] electrolytes

[0135] The electrolyte used in the cylindrical lithium secondary battery of the present invention may include a lithium salt containing LiPF6 and an organic solvent containing ethylene carbonate.

[0136] In addition, if necessary, the electrolyte of the present invention may also include at least one organic solvent selected from cyclic carbonate organic solvents, straight-chain carbonate organic solvents, straight-chain ester organic solvents, and cyclic ester organic solvents.

[0137] Cyclic carbonate organic solvents are high-viscosity organic solvents. Cyclic carbonate organic solvents typically include at least one organic solvent selected from the group consisting of propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate, and vinylene carbonate.

[0138] In addition, linear carbonate organic solvents are organic solvents with low viscosity and low dielectric constant. Typical examples of linear carbonate organic solvents may be at least one organic solvent selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methyl propyl carbonate and ethyl propyl carbonate, and linear carbonate organic solvents may specifically include at least one of ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC).

[0139] Specific examples of straight-chain ester organic solvents may be at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0140] Cyclic ester organic solvents may include at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone.

[0141] In order to improve battery life characteristics, suppress battery capacity reduction and increase battery discharge capacity, the electrolyte may further include other additives in addition to the electrolyte components.

[0142] Typical examples of these other additives may include at least one other additive selected from the group consisting of cyclic carbonates, halogenated carbonates, sulfonyl lactones, sulfates / salts, borates / salts, nitriles, benzenes, amines, silanes, and lithium salts that are different from the lithium salts contained in the electrolyte.

[0143] Specifically, other additives may include those selected from vinylene carbonate (VC), vinyl ethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sulpholactone (PS), 1,4-butane sulpholactone, ethane sulpholactone, 1,3-propene sulpholactone (PRS), 1,4-butene sulpholactone, 1-methyl-1,3-propene sulpholactone, ethylene sulfate (Esa), trimethylene sulfate (TMS), methyltrimethylene sulfate (MTMS), tetraphenylborate, lithium oxaloyl difluoroborate, succinate, adiponitrile, acetonitrile, propionitrile, butyronitrile, valerate, octanoic acid, heptacyanate, etc. Compounds comprising one or more of the following groups: cyclopentadienyl nitrile, cyclohexadienyl nitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, fluorobenzene, triethanolamine, ethylenediamine, tetravinylsilane, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), LiPO2F2, LiODFB, LiBOB (lithium bis(oxalate)borate, LiB(C2O4)2), and LiBF4.

[0144] Based on the total weight of the electrolyte, other additives may be included in an amount from 0.01 wt% to 20 wt%, and preferably in an amount from 0.05 wt% to 5.0 wt%. If the amount of other additives is less than 0.01 wt%, the effect of improving the low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery is not significant. If the amount of other additives is greater than 20 wt%, there is a possibility that excessive side reactions may occur in the electrolyte during battery charging and discharging. In particular, when an excessive amount of additives for SEI layer formation is added, since other additives may not decompose sufficiently at high temperatures, they may exist in the electrolyte at room temperature as unreacted substances or precipitates. Therefore, side reactions that reduce the life or resistance characteristics of the secondary battery may occur.

[0145] exist Figure 4 In the battery casing 142, the uncoated portion 146b of the negative electrode is electrically connected and acts as the negative terminal, which contacts an external power source to transfer current applied from the external power source to the negative electrode.

[0146] In this configuration, the battery housing 142 is a cylindrical container with an opening at the top, and it is formed of a conductive metallic material such as aluminum or steel. The battery housing houses the electrode assembly 141 within its internal space through the opening at the top, and also houses the electrolyte (not shown).

[0147] If necessary, a rolled edge 147 and a crimped portion 148 may be included at the upper end of the battery housing 142. The rolled edge 147 can be formed by pressing the outer peripheral surface of the battery housing 142 into the distance D1. The rolled edge 147 prevents the electrode assembly 141 housed inside the battery housing 142 from escaping through the upper opening of the battery housing 142, and can also act as a support for stably placing the sealing body 143.

[0148] The crimping portion 148 may be formed on the upper part of the rolled edge portion 147 and has an extended and curved shape to surround the outer peripheral surface of the cover plate 143a disposed on the rolled edge portion 147 and a portion of the upper surface of the cover plate 143a.

[0149] Next, a sealing body 143 is used to seal the open end of the battery housing 142, comprising a cover plate 143a and a first gasket 143b. The first gasket 143b provides an airtight seal and insulation between the cover plate 143a and the battery housing 142, and may further include a connecting plate 143c electrically and mechanically connected to the cover plate 143a if necessary. The cover plate 143a can be pressed onto a rolled edge 147 formed in the battery housing 142 and can be secured by a crimping portion 148.

[0150] The cover plate 143a is a component formed of a conductive metallic material, which covers the upper opening of the battery casing 142. The cover plate 143a is electrically connected to the positive terminal of the electrode assembly 141 and is electrically insulated from the battery casing 142 by a first gasket 143b. Therefore, the cover plate 143a can serve as the positive terminal of a cylindrical secondary battery. The cover plate 143a may include a protrusion 143d projecting upward from the center C, and the protrusion 143d can contact an external power source to allow current to be applied from an external power source.

[0151] The first gasket 143b can be disposed between the cover plate 143a and the crimping part 148 to ensure the airtightness of the battery housing 142 and to electrically insulate the battery housing 142 and the cover plate 143a.

[0152] If necessary, the cylindrical battery 140 of the present invention may further include current collectors 144 and 145. The current collectors are respectively coupled to the uncoated portion 146a of the positive electrode and the uncoated portion 146b of the negative electrode, and connected to the electrode terminals (i.e., the positive terminal and the negative terminal).

[0153] Specifically, the cylindrical battery 140 of the present invention may include a first current collector 144 attached to the upper part of the electrode assembly 141 and a second current collector 145 attached to the lower part of the electrode assembly 141.

[0154] It may further include a first collector plate 144 and / or a second collector plate 145.

[0155] A first current collector 144 is attached to the upper part of the electrode assembly 141. The first current collector 144 is formed of a conductive metal material such as aluminum, copper, and nickel, and is electrically connected to the uncoated portion 146a of the positive electrode. A lead 149 can be connected to the first current collector 144. The lead 149 can extend upward from the electrode assembly 141 and can be attached to a connecting plate 143c or directly to the lower surface of the cover plate 143a. The lead 149 and other components can be joined by welding. Preferably, the first current collector 144 can be integrally formed with the lead 149. In this case, the lead 149 can have a long plate shape extending outward from the center of the first current collector 144.

[0156] The first current collector 144 is bonded to the end of the uncoated portion 146a of the positive electrode. The bonding can be performed, for example, by methods such as laser welding, resistance welding, ultrasonic welding, and brazing.

[0157] The second current collector 145 is attached to the lower part of the electrode assembly 141. The second current collector 145 is formed 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 can be attached to the uncoated portion 146b of the negative electrode, and the opposite surface can be attached to the inner bottom surface of the battery casing 142. In this case, the attachment can be performed by methods such as laser welding, resistance welding, ultrasonic welding, and brazing.

[0158] If necessary, the cylindrical battery 140 of the present invention may further include an insulator 146. The insulator 146 may be configured to cover the upper surface of the first current collector 144. Since the insulator 146 covers the first current collector 144, direct contact between the first current collector 144 and the inner peripheral surface of the battery casing 142 can be prevented.

[0159] The insulator 146 includes a lead hole 151, allowing a lead 149 extending upward from the first current collector 144 to be led out. The lead 149 is led out upward through the lead hole 151 and coupled to the lower surface of the connecting plate 143c or the lower surface of the cover plate 143a.

[0160] The insulator 146 may be formed from an insulating polymer resin (e.g., polymer resin materials such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate).

[0161] If necessary, the cylindrical battery 140 of the present invention may further include an vent 152 formed on the lower surface of the battery casing 142. The vent 152 corresponds to a region on the lower surface of the battery casing 142 that is thinner than the surrounding area. Because the vent 152 is thinner, it is structurally weaker than the surrounding area. Therefore, if the pressure in the cylindrical battery 140 increases to a certain level, the vent 152 ruptures and the gas in the battery casing 142 can be discharged to the outside, thereby preventing the battery from exploding.

[0162] exist Figure 5 A cross-sectional view of a cylindrical battery with a tabless structure according to another embodiment of the present invention is shown. In the following text, reference will be made to... Figure 5 A cylindrical battery according to another embodiment of the present invention is described. However, Figure 5 Only one embodiment of the present invention has been shown, and the structure of the cylindrical battery of the present invention is not limited to this. Figure 5 The scope of public disclosure.

[0163] Reference Figure 5 Another embodiment of the cylindrical battery 170 of the present invention and Figure 4The cylindrical battery 140 shown has a different battery casing and sealing structure compared to the one shown, but has substantially the same electrode assembly and electrolyte construction.

[0164] Specifically, the cylindrical battery 170 includes a battery housing 171 through which a rivet terminal 172 is mounted. The rivet terminal 172 is mounted on a closed surface (the upper surface in the figure) that is partially closed at one end of the battery housing 171. The rivet terminal 172 is riveted to a through hole (the first opening at the first end) in the battery housing 171 with an insulating second washer 173 disposed therebetween. The rivet terminal 172 protrudes to the outside in a direction opposite to the direction of gravity.

[0165] The rivet terminal 172 includes a terminal protrusion 172a and a terminal insertion portion 172b. The terminal protrusion 172a protrudes to the outside of the closed surface of the battery housing 171. The terminal protrusion 172a may be located approximately at the center of a portion of the closed surface of the battery housing 171. The maximum diameter of the terminal protrusion 172a may be larger than the maximum diameter of the through hole formed in the battery housing 171. The terminal insertion portion 172b may pass through approximately the center of the closed surface of the battery housing 171 and be electrically connected to the uncoated portion 146a of the positive electrode. The terminal insertion portion 172b may be riveted to the inner surface of the battery housing 171. That is, the end of the terminal insertion portion 172b may have a shape that bends toward the inner surface of the battery housing 171. The maximum diameter of the end of the terminal insertion portion 172b may be larger than the maximum diameter of the through hole in the battery housing 171.

[0166] The lower end surface of the terminal insertion portion 172b can be welded to the first current collector 144, which is connected to the uncoated portion 146a of the positive electrode. An insulating cap 174, formed of insulating material, can be disposed between the first current collector 144 and the inner surface of the battery casing 171. The insulating cap 174 covers the upper part of the first current collector 144 and the upper edge of the electrode assembly 141. Therefore, this can prevent short circuits caused by contact between the outer peripheral uncoated portion of the electrode assembly 141 and the inner surface of the battery casing 171, which has a different polarity. The terminal insertion portion 172b of the rivet terminal 172 can pass through the insulating cap 174 to be welded to the first current collector 144.

[0167] A second washer 173 is disposed between the battery housing 171 and the rivet terminal 172 to prevent electrical contact between the battery housing 171 and the rivet terminal 172, which have opposite polarities. Therefore, the upper surface of the battery housing 171, which has a substantially flat shape, can serve as the positive terminal of the cylindrical battery 170.

[0168] The second washer 173 includes a washer protrusion 173a and a washer insertion portion 173b. The washer protrusion 173a is disposed between the terminal protrusion 172a of the rivet terminal 172 and the battery housing 171. The washer insertion portion 173b is disposed between the terminal insertion portion 172b of the rivet terminal 172 and the battery housing 171. The washer insertion portion 173b can deform together with the terminal insertion portion 172b during riveting to tightly adhere to the inner surface of the battery housing 171. The second washer 173 can be formed, for example, from an insulating polymer resin.

[0169] The washer protrusion 173a of the second washer 173 may have an extended shape to cover the outer peripheral surface of the terminal protrusion 172a of the rivet terminal 172. With the second washer 173 covering the outer peripheral surface of the rivet terminal 172, short circuits can be prevented during the bonding of electrical connection components, such as busbars, to the upper surface of the battery housing 171 and / or the rivet terminal 172. Although not shown in the figures, the washer protrusion 173a may have an extended shape to cover not only the outer peripheral surface of the terminal protrusion 172a but also a portion of its upper surface.

[0170] When the second gasket 173 is formed of polymer resin, it can be heat-fused to the battery housing 171 and the rivet terminal 172. This enhances the airtightness at the interface between the second gasket 173 and the rivet terminal 172, as well as at the interface between the second gasket 173 and the battery housing 171. When the gasket protrusion 173a of the second gasket 173 has a shape extending to the upper surface of the terminal protrusion 172a, the rivet terminal 172 can be integrally bonded to the second gasket 173 via injection molding.

[0171] The area 175 on the upper surface of the battery casing 171, excluding the area occupied by the rivet terminal 172 and the second washer 173, corresponds to the negative terminal with the polarity opposite to that of the rivet terminal 172.

[0172] The second current collector 176 is attached to the lower part of the electrode assembly 141. The second current collector 176 is formed of a conductive metal material such as aluminum, steel, copper and nickel, and is electrically connected to the uncoated portion 146b of the negative electrode.

[0173] Preferably, the second current collector 176 is electrically connected to the battery housing 171. For this purpose, at least a portion of the edge of the second current collector 176 can be fixed by being disposed between the inner surface of the battery housing 171 and the first washer 178b. In one example, at least a portion of the edge of the second current collector 176 can be fixed to the rolled edge 180 by welding while being supported on the lower end surface of the rolled edge 180 formed at the lower end of the battery housing 171. In a variant example, at least a portion of the edge of the second current collector 176 can be directly welded to the inner wall surface of the battery housing 171.

[0174] The second manifold 176 may have a plurality of irregularities (not shown) radially formed on the surface facing the uncoated portion 146b. When irregularities are formed, the second manifold 176 may be pressed to press the irregularities into the uncoated portion 146b.

[0175] Preferably, the ends of the second manifold 176 and the uncoated portion 146b can be joined by welding, for example, laser welding.

[0176] The sealing body 178 at the lower opening end of the sealed battery housing 171 includes a cover plate 178a and a first washer 178b. The first washer 178b electrically separates the cover plate 178a and the battery housing 171. A crimping portion 181 secures the edge of the cover plate 178a and the first washer 178b together. The cover plate 178a includes a venting portion 179. The structure of the venting portion 179 is substantially the same as that of the embodiment described above.

[0177] Preferably, the cover plate 178a is formed of a conductive metal material. However, since the first gasket 178b is disposed between the cover plate 178a and the battery housing 171, the cover plate 178a is not polarized. The seal 178 is used to seal the lower opening of the battery housing 171 and to release gas when the internal pressure of the battery cell 170 increases above a critical value.

[0178] Preferably, the rivet terminal 172, which is electrically connected to the uncoated portion 146a of the positive electrode, serves as the positive terminal. Furthermore, the portion 175 of the upper surface of the battery casing 171, excluding the rivet terminal 172, which is electrically connected to the uncoated portion 146b of the negative electrode via the second current collector 176, serves as the negative terminal. As described above, when both electrode terminals are located at the top of the cylindrical battery, electrical connection components such as busbars can be provided only on one side of the cylindrical battery 170.

[0179] This leads to a simplification of the battery pack structure and an increase in energy density. Furthermore, since the portion 175 used as the negative terminal has a substantially flat shape, sufficient contact area can be ensured for incorporating electrical connection components such as busbars. Therefore, the cylindrical battery 170 can reduce the resistance at the contact points of the electrical connection components to a desired level.

[0180] When a cylindrical lithium secondary battery is formed with a tabless structure as described above, the battery with a tabless structure has a smaller current concentration than a conventional battery with electrode tabs, which can effectively reduce the heat generation in the battery and thus improve the thermal stability of the battery.

[0181] The cylindrical lithium secondary battery of the present invention, as described above, can be used to prepare battery packs. Figure 6 The structure of a battery pack according to an embodiment of the present invention is schematically illustrated. (Refer to...) Figure 6 The battery pack 3 of this embodiment includes: an assembly electrically connected to a cylindrical secondary battery 1 and a battery pack housing 2 housing the assembly. The cylindrical secondary battery 1 is the battery cell of the above embodiment. In the drawings, for ease of explanation, components such as busbars for electrically connecting the cylindrical secondary battery 1, cooling units, and external terminals are omitted.

[0182] Battery pack 3 can be installed in a vehicle. The vehicle can be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle can be a four-wheeled vehicle or a two-wheeled vehicle.

[0183] The invention will be described in more detail below with reference to specific embodiments.

[0184] Example 1.

[0185] (Electrolyte preparation)

[0186] LiPF6 was added to a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75, so that the concentration of LiPF6 was 1.3M, thereby preparing an electrolyte (ethylene carbonate content: 19.17 wt% / LiPF6 content: 15.41 wt%) (see Table 1 below).

[0187] (Preparation of secondary batteries)

[0188] The positive electrode active material (Li(Ni) 0.90 Mn 0.03 Co 0.05 Al 0.02 O2) (It is in single-particle form and has an average particle size D) 50 A positive electrode slurry was prepared by adding and mixing carbon nanotubes and PVDF binder in an N-methylpyrrolidone mixture at a weight ratio of 97.8:0.6:1.6. The positive electrode slurry was then coated onto one surface of an aluminum current collector, dried at 120°C, and then rolled to prepare a positive electrode plate.

[0189] A negative electrode slurry was prepared by adding the negative electrode active material (graphite and SiO = 95:5 by weight), a conductive agent (super C), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) to water in a weight ratio of 96:2:1.5:0.5. The negative electrode slurry was then coated onto one surface of a copper current collector sheet, dried at 150°C, and then rolled to prepare the negative electrode plate.

[0190] A separator is placed between the prepared positive and negative electrode plates, stacked in the order of separator / positive electrode plate / separator / negative electrode plate, and then wound to prepare an electrode assembly (core diameter: 7 mm). The electrode assembly prepared as described above is inserted into a cylindrical battery can (diameter: 46 mm / height: 80 mm), and then electrolyte (38 g) is injected to prepare a 4680 cell (shape factor ratio: 0.575).

[0191] Example 2.

[0192] (Preparation of secondary batteries)

[0193] Except for the electrolyte (31g) injected in Example 1, the electrolyte and the 4680 cell containing it (shape factor ratio: 0.575) were prepared in the same manner as in Example 1.

[0194] Example 3.

[0195] (Electrolyte preparation)

[0196] LiPF6 was added to a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75, so that the concentration of LiPF6 was 1.2M, thereby preparing an electrolyte (ethylene carbonate content: 19.40 wt% / LiPF6 content: 14.43 wt%) (see Table 1 below).

[0197] (Preparation of secondary batteries)

[0198] In addition to injecting the electrolyte (38g) prepared above, the electrolyte and the 4680 cell containing it were prepared in the same manner as in Example 1.

[0199] Example 4.

[0200] (Preparation of secondary batteries)

[0201] Except for injecting the electrolyte (31g) of Example 3, the electrolyte and the 4680 cell containing it (shape factor ratio: 0.575) were prepared in the same manner as in Example 3.

[0202] Example 5.

[0203] (Electrolyte preparation)

[0204] LiPF6 was added to a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75, so that the concentration of LiPF6 was 1.05M, thereby preparing an electrolyte (ethylene carbonate content: 19.76 wt% / LiPF6 content: 14.40 wt%) (see Table 1 below).

[0205] (Preparation of secondary batteries)

[0206] In addition to injecting the electrolyte (31g) prepared above, the electrolyte and the 4680 cell containing it were prepared in the same manner as in Example 1.

[0207] Example 6.

[0208] (Electrolyte preparation)

[0209] LiPF6 was added to a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75 to make the concentration of LiPF6 1.2 M. Then, 3 wt% of ethylene carbonate (VC) and 0.5 wt% of 1,3-propanesulfonyl lactone (1,3-PS) were added to prepare an electrolyte (ethylene carbonate content: 19.40 wt% / LiPF6 content: 14.43 wt%) (see Table 1 below).

[0210] (Preparation of secondary batteries)

[0211] In addition to injecting the electrolyte (38g) prepared above, the electrolyte and the 4680 cell containing it were prepared in the same manner as in Example 1.

[0212] Example 7.

[0213] (Electrolyte preparation)

[0214] LiPF6 was added to a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75 to make the concentration of LiPF6 1.2M. Then, 3 wt% ethylene carbonate (VC), 0.5 wt% 1,3-propanesulfonyl lactone (1,3-PS), and 1 wt% fluoroethylene carbonate (FEC) were added to prepare an electrolyte (ethylene carbonate content: 19.17 wt% / LiPF6 content: 14.40 wt%) (see Table 1 below).

[0215] (Preparation of secondary batteries)

[0216] In addition to injecting the electrolyte (38g) prepared above, the electrolyte and the 4680 cell containing it were prepared in the same manner as in Example 1.

[0217] Example 8.

[0218] (Electrolyte preparation)

[0219] LiPF6 was added to a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75 to make the concentration of LiPF6 1.2M. Then, 3% by weight of ethylene carbonate (VC) and 0.5% by weight of ethylene sulfate (Esa) were added to prepare an electrolyte (ethylene carbonate content: 19.40% by weight / LiPF6 content: 14.43% by weight) (see Table 1 below).

[0220] (Preparation of secondary batteries)

[0221] In addition to injecting the electrolyte (38g) prepared above, the electrolyte and the 4680 cell containing it were prepared in the same manner as in Example 1.

[0222] Comparative Example 1.

[0223] (Preparation of secondary batteries)

[0224] Except for injecting the electrolyte (43g) of Example 3, the electrolyte and the 4680 cell containing it (shape factor ratio: 0.575) were prepared in the same manner as in Example 3.

[0225] Compare Example 2.

[0226] (Preparation of secondary batteries)

[0227] Except for injecting the electrolyte (25g) of Example 3, the electrolyte and the 4680 cell containing it (shape factor ratio: 0.575) were prepared in the same manner as in Example 3.

[0228] Comparative Example 3.

[0229] (Electrolyte preparation)

[0230] LiPF6 was added to a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75, so that the concentration of LiPF6 was 0.95M, thereby preparing an electrolyte (ethylene carbonate content: 20.00 wt% / LiPF6 content: 11.89 wt%) (see Table 1 below).

[0231] (Preparation of secondary batteries)

[0232] In addition to injecting the electrolyte (31g) prepared above, the electrolyte and the 4680 cell including it were prepared in the same manner as in Example 1.

[0233] Comparative Example 4.

[0234] (Electrolyte preparation)

[0235] LiPF6 was added to a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75, so that the concentration of LiPF6 was 1.6M, thereby preparing an electrolyte (ethylene carbonate content: 18.50 wt% / LiPF6 content: 17.73 wt%) (see Table 1 below).

[0236] (Preparation of secondary batteries)

[0237] In addition to injecting the electrolyte (38g) prepared above, the electrolyte and the 4680 cell containing it were prepared in the same manner as in Example 1.

[0238] Comparative Example 5.

[0239] (Electrolyte preparation)

[0240] LiPF6 was added to a non-aqueous organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 20:5:75, so that the concentration of LiPF6 was 1.3M, thereby preparing an electrolyte (ethylene carbonate content: 19.17 wt% / LiPF6 content: 15.41 wt%) (see Table 1 below).

[0241] (Preparation of secondary batteries)

[0242] The positive electrode active material (Li(Ni) 0.90 Mn 0.03 Co 0.05 Al 0.02 O2) (It is in single-particle form and has an average particle size D) 50 A positive electrode slurry was prepared by adding and mixing carbon nanotubes and PVDF binder in an N-methylpyrrolidone mixture at a weight ratio of 97.8:0.6:1.6. The positive electrode slurry was then coated onto one surface of an aluminum current collector, dried at 120°C, and then rolled to prepare a positive electrode plate.

[0243] A negative electrode slurry was prepared by adding the negative electrode active material (graphite and SiO = 95:5 by weight), a conductive agent (super C), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) to water in a weight ratio of 96:2:1.5:0.5. The negative electrode slurry was then coated onto one surface of a copper current collector sheet, dried at 150°C, and then rolled to prepare the negative electrode plate.

[0244] A separator is placed between the prepared positive and negative electrode plates, stacked in the order of separator / positive electrode plate / separator / negative electrode plate, and then wound to prepare an electrode assembly (core diameter: 7 mm). The electrode assembly prepared as described above is inserted into a cylindrical battery can (diameter: 46 mm / height: 70 mm), and then electrolyte (38 g) is injected to prepare a 4670 cell (shape factor ratio: 0.657).

[0245] Comparative Example 6.

[0246] (Preparation of secondary batteries)

[0247] Except that the prepared electrode assembly (diameter of the core: 7 mm) was inserted into the cylindrical battery can (diameter: 46 mm, height: 120 mm) and then the electrolyte (38 g) was injected, the 46120 cell (shape factor ratio: 0.383) was prepared in the same manner as Comparative Example 5.

[0248] [Table 1]

[0249]

[0250] In Table 1 above, mathematical expression (1)* represents the expression derived from... The calculated value.

[0251] Experimental Example

[0252] Experimental Example 1. Evaluation of AC Resistance

[0253] After forming the secondary batteries prepared in Examples 1, 3, 5, 6, and 8, and the secondary batteries prepared in Comparative Examples 1 to 4 and 6, respectively, at a current of 25 A (0.1 C) and 25 °C for two cycles (charging: 4.2 V CC, discharging: 2.5 V CC), constant current / constant voltage (CC / CV) charging and CC discharging at 2.5 V and 8.33 A (0.3 C, 0.05 C cutoff) were repeated three times. Subsequently, the AC resistance was measured using a multi-impedance analyzer (Biologic, model: VMP3) at 30% SOC (state of charge) and 25 °C in the range of 1 kHz. The results are presented in Table 2 below.

[0254] Experiment Example 2. Evaluation of DC Resistance (Internal DC Resistance)

[0255] The secondary batteries prepared in Examples 1, 3, 5, 6 and 8, and the secondary batteries prepared in Comparative Examples 1 to 4 and 6, were formed in the same manner as in Experimental Example 1 and the cycle was repeated three times. Each secondary battery was then fully charged at 4.2V and 8.33A (0.3C, 0.05C cutoff) and then discharged to 50% SOC at room temperature. The voltage drop generated when discharged at a current of 0.5C for 10 seconds was recorded. The DC resistance (DC-IR) value was measured using Ohm's law (R = V / I). The results are shown in Table 2 below.

[0256] [Table 2]

[0257] ACIR(mOhm) DCIR(mOhm) Example 1 97 95 Example 3 95 93 Example 5 97 87 Example 6 95 93 Example 8 96 92 Comparative Example 1 100 100 Comparative Example 2 115 130 Comparative Example 3 118 121 Comparative Example 4 102 105 Comparative Example 6 120 135

[0258] Referring to Table 2, for the secondary batteries prepared in Examples 1, 3, 5, 6 and 8, since the increase in resistance was suppressed, it can be considered that the cell performance was improved compared with the secondary batteries prepared in Comparative Examples 1 to 4 and 6.

[0259] That is, when comparing the cells of Examples 3, 6 and 8 with the cells of Comparative Examples 1 and 2, even if the cell size and electrolyte composition are the same, for the cells of Comparative Examples 1 and 2 (where the value calculated by mathematical formula (1) considering the amount of electrolyte injected deviates from the conditions of the present invention), it can be considered that the cell performance is worse than that of the cells of Examples 3, 6 and 8 due to the increased resistance.

[0260] Furthermore, when comparing the secondary battery prepared in Example 1 with the secondary battery prepared in Comparative Example 4, even with the same cell size and electrolyte composition, for the cell of Comparative Example 4 (where the value calculated by mathematical formula (1) considering the amount of lithium salt and ethylene carbonate contained in the electrolyte deviates from the conditions of the present invention), it can be considered that the cell performance is worse than that of the cell of Example 1 due to the increased resistance.

[0261] Furthermore, when comparing the secondary battery prepared in Example 5 with the secondary battery prepared in Comparative Example 3, even with the same cell size and electrolyte composition, for the cell of Comparative Example 3 (where the value calculated by mathematical formula (1) considering the amount of lithium salt and ethylene carbonate contained in the electrolyte deviates from the conditions of the present invention), it can be considered that the cell performance is worse than that of the cell of Example 5 due to the increased resistance.

[0262] For the secondary battery of Comparative Example 6, even when the cell size and electrolyte composition are the same as those of Example 1, the resistance increases compared to the secondary battery of the Example because the amount of electrolyte injected is insufficient when the form factor ratio exceeds the range of the present invention, resulting in reduced wettability.

[0263] Experimental Example 3.

[0264] The initial capacity was measured after each cell prepared in Examples 1 to 8 and Comparative Examples 1 to 6 was charged to 4.2V at a constant current-constant voltage rate of 1.0C at room temperature (25°C) and then discharged at a cutoff rate of 0.5C.

[0265] Subsequently, a cycle was defined as charging to 4.2V at a constant current-constant voltage rate of 1.0C at a high temperature (40°C) and then discharging to 2.5V at a C rate of 0.2C, and 100 charge-discharge cycles were performed. The capacity retention rate after 100 cycles at 40°C relative to the initial capacity after the first cycle was measured, and the results are presented in Table 3 below.

[0266] [Table 3]

[0267] Capacity retention (%) after 100 cycles Example 1 95 Example 2 98 Example 3 93 Example 4 97 Example 5 96 Example 6 93 Example 7 95 Example 8 94 Comparative Example 1 <80 Comparative Example 2 <80 Comparative Example 3 90 Comparative Example 4 85 Comparative Example 5 89 Comparative Example 6 87

[0268] Referring to Table 3, for the lithium secondary batteries of Examples 1 to 8 of the present invention, it can be considered that the capacity retention rate after 100 cycles is significantly improved compared with the lithium secondary batteries of Comparative Examples 1 to 6.

[0269] Symbol Explanation

[0270] 10: Positive electrode 11: Negative electrode

[0271] 12: Diaphragm; 20: Current collector

[0272] 21, 21a: Active material layer; 22, 22a, 22c: Uncoated area

[0273] 24: Insulation layer

[0274] 140, 170: Cylindrical batteries

[0275] 141: Jelly Roll-Type Electrode Assembly

[0276] 142, 171: Battery casing

[0277] 143, 178: Sealing body

[0278] 144: First manifold; 145, 176: Second manifold

[0279] 146a: Uncoated portion of the positive electrode plate

[0280] 146b: Uncoated portion of the negative electrode plate

[0281] 146: Insulator 152: Exhaust section

[0282] 172: Rivet Terminal

[0283] 173: Second washer; 178b: First washer

[0284] 173a: Exposed washer portion; 173b: Inserted washer portion

[0285] 147, 180: Crimped edge; 148: Pressed edge.

[0286] 149: Lead wire 172a: Exposed terminal portion

[0287] 173b: Terminal insertion part; 174: Insulating cap

Claims

1. A lithium secondary battery, comprising: Battery casing; Electrode assembly housed within the battery casing; And electrolytes, The electrode assembly includes a positive electrode containing a positive active material, a separator, and a negative electrode containing a negative active material. The positive electrode active material is a lithium transition metal oxide containing nickel (Ni) and cobalt (Co). The lithium transition metal oxide satisfies mathematical formula (2), and The electrolyte comprises LiPF6 as a lithium salt and ethylene carbonate as an organic solvent. Wherein, the ratio of the diameter (r) to the height (h) of the battery casing of the lithium secondary battery, i.e., the shape factor ratio, is 0.4 or more, and satisfies the condition of mathematical formula (1): [Mathematical expression (1)] In mathematical formula (1), h is the height of the battery casing in mm. r is the diameter of the battery casing, measured in millimeters. W LiPF6 The amount of LiPF6 is expressed as a percentage (%) relative to the total weight of the electrolyte. W EC It is the amount of ethylene carbonate relative to the total weight of the electrolyte, expressed as a percentage (%). W EL This indicates the total weight of the electrolyte contained in a lithium secondary battery, expressed in grams. Mathematical expression (2): 18≤X Ni / X Co ≤48 In mathematical expression (2), X Ni X is the molar percentage of Ni in all metals other than lithium in the lithium transition metal oxide. Co It is the molar percentage of Co in all metals other than lithium in the lithium transition metal oxide.

2. The lithium secondary battery according to claim 1, wherein, The lithium secondary battery is a cylindrical battery with a shape factor ratio of 0.4 to 0.6, where the ratio of the diameter (r) to the height (h) of the battery casing is 0.4 to 0.

6.

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

4. 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 where no active material layer is formed, and is a battery with a tabless structure, wherein the uncoated portion of the positive electrode or the uncoated portion of the negative electrode is defined as an electrode tab.

5. The lithium secondary battery according to claim 4, wherein, The uncoated portions of the positive electrode and the negative electrode are respectively formed on one side end of the positive electrode and the negative electrode along the winding direction of the electrode assembly. The current collector is combined with the uncoated portions of the positive electrode and the negative electrode respectively, and the current collector is connected to the electrode terminal.

6. The lithium secondary battery according to claim 5, wherein, The uncoated portions of the positive electrode and the uncoated portions of the negative electrode are processed into multiple independently bendable segments, and At least a portion of the plurality of segments bends toward the winding center of the electrode assembly.

7. The lithium secondary battery according to claim 6, wherein, At least a portion of the curved plurality of segments overlaps the upper and lower ends of the electrode assembly, and the current collector is incorporated into the overlapping plurality of segments.

8. The lithium secondary battery according to claim 1, wherein, The lithium transition metal oxide is represented by chemical formula 1. [Chemical Formula 1] Li a Ni b Co c M 1 d M 2 e O2 In chemical formula 1, M 1 is manganese (Mn), aluminum (Al), or a combination thereof, M 2 is at least one selected from the group consisting of zirconium (Zr), tungsten (W), yttrium (Y), barium (Ba), calcium (Ca), titanium (Ti), magnesium (Mg), tantalum (Ta), and niobium (Nb), and 0.8 ≤ a ≤ 1.2, 0.85 < b < 1, 0 < c < 0.06, 0 < d < 0.15, and 0 ≤ e ≤ 0.

1.

9. The lithium secondary battery according to claim 8, wherein, The lithium transition metal oxide is Li(Ni) 0.90 Mn 0.05 Co 0.05 O2, Li(Ni) 0.94 Co 0.04 Mn 0.02 O2, Li(Ni) 0.87 Mn 0.07 Co 0.04 Al 0.02 O2 or Li(Ni) 0.90 Mn 0.03 Co 0.05 Al 0.02 )O2.

10. The lithium secondary battery according to claim 1, wherein, The negative electrode active material is a mixture of carbon-based and silicon-based negative electrode active materials, and The carbon-based anode active material and the silicon-based anode active material are contained in a weight ratio of 95:5 to 99:

1.

11. The lithium secondary battery according to claim 1, wherein, W LiPF6 12% to 16% by weight, W EC 13% to 25% by weight, W EL The dosage is 30g to 50g.

12. A battery pack comprising a lithium secondary battery according to any one of claims 1 to 11.

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