Cylindrical lithium secondary battery

Abstract

The present invention provides a lithium secondary battery including: a battery case; an electrode assembly housed inside the battery case; and an electrolyte, wherein the electrode assembly includes a positive electrode including a positive electrode active material, a separator, and a negative electrode including a negative electrode active material, the electrolyte includes LiPF6 as a lithium salt and ethylene carbonate as an organic solvent, and the lithium secondary battery has a ratio of a diameter (R) to a height (H) (form factor ratio) of a battery case of 0.4 or more, and satisfies a condition of the following formula (1): [Formula (1)] (in formula (1), H is the height (mm) of the battery case, R is the diameter (mm) of the battery case, WLiPF6 is a percentage (%) of the content of LiPF6 with respect to the total weight of the electrolyte, WEC is a percentage (%) of the content of ethylene carbonate with respect to the total weight of the electrolyte, and WEL means the weight (g) of the total electrolyte included in the lithium secondary battery).

Description

cylindrical lithium secondary battery

[0001] Technology field

[0002] The present invention relates to a lithium secondary battery, and more particularly, to a cylindrical lithium secondary battery having improved high-temperature durability and long-life characteristics.

[0003]

[0004] Cross-citation with related application(s)

[0005] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0093983, filed July 19, 2023, and Korean Patent Application No. 10-2024-0095334, filed July 18, 2024, the entire contents of which are incorporated herein by reference.

[0006] With technological advancements in electric vehicles, portable electronic devices, and other devices, the demand for lithium secondary batteries as an energy source is rapidly increasing.

[0007] Lithium secondary batteries can be classified into cylindrical, prismatic, and pouch-type batteries depending on the shape of the battery case. Among these, cylindrical batteries are manufactured by sequentially stacking sheet-shaped positive electrodes, separators, and negative electrodes in a cylindrical battery case, winding them in one direction to form a jelly-roll-type electrode assembly, and then covering the top of the battery case with a cap plate to seal it. The positive and negative electrodes are each provided with strip-shaped positive and negative electrode tabs, and the positive and negative electrode tabs are connected to electrode terminals and electrically connected to an external power source. For reference, the positive electrode terminal is the cap plate, and the negative electrode terminal is the battery case. However, in the case of a conventional cylindrical battery with such a structure, there is a problem that the current is concentrated on the strip-shaped electrode tabs, resulting in high resistance, a lot of heat generation, and poor current collection efficiency.

[0008] However, resistance and heat generation were not major issues for small cylindrical secondary batteries with form factors such as 18650 (cylindrical secondary battery with a diameter of 18 mm × height of 65 mm) or 21700 (cylindrical secondary battery with a diameter of 21 mm × height of 70 mm), which were mainly used in the past.

[0009] However, in recent years, as electric vehicles require increased driving range and faster charging speeds, the development and use of larger form factors, such as 46800 (a cylindrical secondary battery with a diameter of 46 mm and a height of 80 mm), are being considered. In addition, in order to improve the rapid charging characteristics of such large cylindrical secondary batteries, a so-called tab-less cylindrical secondary battery has been proposed, which utilizes the current collectors themselves of the non-conductive portions of the positive and negative electrodes as electrode tabs instead of using separate electrode tabs in the form of strips.

[0010] The enlarged cylindrical secondary battery having the above tab-less structure can not only exhibit relatively high capacity characteristics and energy density, but also has the advantage of increasing the production efficiency of cylindrical secondary batteries for electric vehicles and reducing their production cost. In addition, by applying the tab-less structure, the number of parts is reduced, the electrical connection (contact) area between the electrode tab and the electrode terminal is increased, and the electron movement distance is shortened, thereby improving the output characteristics and dissipating the heat generated during the charging and discharging processes.

[0011] However, since the large-sized cylindrical secondary battery applying the tab-less structure, etc. performs a process of compressing the part where the active material layer is not coated in order to provide sufficient weldability with the case and terminal parts, there is a problem that the electrolyte movement path between the positive electrode, separator, and negative electrode inside the wound electrode current collector is blocked, so that the electrolyte movement does not occur properly, resulting in a decrease in electrolyte impregnation property.

[0012] Accordingly, there is an urgent need for the development of technology that can improve electrolyte impregnation properties and thus enhance overall performance in large-sized cylindrical secondary batteries applicable to medium- to large-sized devices such as automobiles.

[0013] The present invention is intended to solve the above-mentioned problems, and relates to a lithium secondary battery capable of implementing excellent high-temperature durability and cycle characteristics by establishing optimal electrolyte impregnation conditions by controlling the electrolyte composition and amount according to the dimensions of a large-sized lithium secondary battery using a tab-less structure, etc.

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

[0015] The above electrode assembly includes a positive electrode including a positive active material, a separator, and a negative electrode including a negative active material,

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

[0017] The above lithium secondary battery provides a lithium secondary battery having a ratio of the diameter (r) to the height (h) of the battery case (form factor ratio) of 0.4 or more and satisfying the condition of the following equation (1):

[0018] [Formula (1)]

[0019] 5.6 ≤ ×100≤8.6

[0020] (In the above equation (1), h is the height of the battery case (mm),

[0021] r is the diameter of the battery case (mm),

[0022] W LiPF6 is the content of LiPF6 in percentage (%) relative to the total weight of the electrolyte,

[0023] W ECis the content of ethylene carbonate in percentage (%) relative to the total weight of the electrolyte.

[0024] W EL refers to the weight (g) of the total electrolyte contained in a lithium secondary battery)

[0025]

[0026] Meanwhile, the lithium secondary battery may be a battery having a tab-less structure including a non-conductive portion in which an active material layer is not formed on at least a portion of the positive electrode and the negative electrode, and in which the non-conductive portion of the positive electrode or the non-conductive portion of the negative electrode is defined as an electrode tab.

[0027] Meanwhile, the positive electrode active material is a lithium transition metal oxide containing Ni and Co, and the lithium transition metal oxide may satisfy the following equation (2).

[0028] Equation (2):

[0029] 18 ≤ X Ni / X Co ≤ 48

[0030] (In the above equation (2), X Ni is the molar percentage of Ni among the total metals excluding lithium in the above lithium transition metal oxide, and X Co is the molar percentage of Co among the total metals excluding lithium in the above lithium transition metal oxide.)

[0031] As in the lithium secondary battery according to the present invention, when the electrolyte composition and amount of electrolyte satisfy specific conditions depending on the dimensions of the battery cell, and the composition ratio of Ni and Co included in the positive electrode active material satisfies specific conditions, optimal electrolyte impregnation conditions can be established, and side reactions at the interface between the positive electrode and the electrolyte can be minimized, thereby realizing excellent high-temperature durability and cycle characteristics.

[0032] Figure 1 is a drawing showing a state of lamination before winding of an electrode assembly according to the present invention.

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

[0034] FIG. 3 is a drawing for explaining the structure of an electrode assembly according to one embodiment of the present invention.

[0035] FIG. 4 is a cross-sectional view showing the structure of a cylindrical battery with a tab-less structure according to one embodiment of the present invention.

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

[0037] Figure 6 is a drawing for explaining a battery pack according to the present invention.

[0038] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0039]

[0040] In the case of large-sized cylindrical lithium secondary batteries that use conventional tab-less structures, there is a disadvantage in that the electrolyte impregnation property is lower than that of small batteries, making it difficult to achieve the desired performance with the same chemistry as small batteries. In particular, when manufacturing large-sized cylindrical secondary batteries, if the amount of electrolyte injected into the limited internal space of the cylindrical cell increases, the internal empty space decreases, which increases the internal pressure. As a result, the gaseous byproducts generated during activation are not discharged outside the electrode assembly but remain inside the electrode assembly, causing the electrolyte to be pushed out of the electrode assembly and reducing wetting. Conversely, if the internal empty space increases due to a decrease in the amount of electrolyte injected, it is difficult for the electrolyte to be impregnated into the electrode assembly, so the wetting property remains disadvantageous. As such, electrolyte wetting property is closely related to cell resistance. That is, if the electrolyte is insufficient or the wetting property is reduced, the problem of increased resistance is caused (Seong Jin An et al 2017 J. Electrochem. Soc. 2017, 164 A1195).

[0041] Accordingly, the inventors of the present invention have conducted repeated research to improve the performance of large-sized cylindrical lithium secondary batteries, and as a result, have found that when an appropriate amount of electrolyte is injected, appropriate impregnation is secured, thereby suppressing an increase in initial cell resistance and improving rapid charge cycle characteristics. To this end, they have found a method for calculating an appropriate amount of electrolyte, thereby completing the present invention.

[0042]

[0043] Hereinafter, a lithium secondary battery according to the present invention will be described in detail.

[0044] Specifically, the present invention relates to a lithium secondary battery comprising a battery case; an electrode assembly housed inside the battery case; and an electrolyte.

[0045] The above electrode assembly includes a positive electrode including a positive active material, a separator, and a negative electrode including a negative active material,

[0046] The above electrolyte contains LiPF6 as a lithium salt and ethylene carbonate as an organic solvent.

[0047] The above lithium secondary battery provides a lithium secondary battery having a ratio of a diameter (r) to a height (h) of a battery case (form factor ratio) of 0.4 or more and satisfying the condition of the following equation (1):

[0048] [Formula (1)]

[0049] 5.6 ≤ ×100≤8.6

[0050] (In the above equation (1), h is the height of the battery case (mm),

[0051] r is the diameter of the battery case (mm),

[0052] W LiPF6 is the content of LiPF6 in percentage (%) relative to the total weight of the electrolyte,

[0053] W EC is the content of ethylene carbonate in percentage (%) relative to the total weight of the electrolyte.

[0054] W EL refers to the weight (g) of the total electrolyte contained in a lithium secondary battery)

[0055]

[0056] Preferably, in the above formula (1), ×100 can be 5.65 to 8.6, more preferably 6.5 to 8.6.

[0057] Above When the value of ×100 satisfies the above range, optimal electrolyte impregnation conditions can be established according to the dimensions of the battery cell, thereby effectively improving the performance of the secondary battery.

[0058] Meanwhile, the lithium secondary battery according to the present invention may be a cylindrical lithium secondary battery having a form factor ratio of 0.4 or more, preferably 0.4 to 0.6.

[0059]

[0060] Meanwhile, in the above equation (1), W EL is the actual amount (g) of the total electrolyte injected into the battery case, which may vary depending on the dimensions and size of the battery cell, but is preferably about 30 g to 50 g in the case of a cylindrical lithium secondary battery having a form factor ratio of 0.4 to 0.6.

[0061] Preferably, in the case of a cylindrical battery having a form factor ratio of 0.4 or more and 0.5 or less, the W EL can be about 35g to 50g. Also, when the form factor ratio is greater than 0.5 and less than or equal to 0.6, the W EL can be about 30g to 40g. Meanwhile, the amount of electrolyte solution (g) (W) injected into the battery case EL ) is somewhat small, the electrolyte impregnation property is reduced, making it difficult to achieve the desired battery performance, and the amount of electrolyte injected into the battery case (g) (W EL ) If there is too much, gas generation, etc. may become severe, which may cause explosion and electrolyte leakage.

[0062]

[0063] In the above equation (1), W LiPF6 The content of LiPF6 is expressed as a percentage (%) of the total weight of the electrolyte during the manufacture of the electrolyte, and the viscosity of the electrolyte can be controlled according to the content of LiPF6.

[0064] Specifically, when manufacturing an electrolyte applicable to a cylindrical lithium secondary battery having a form factor ratio of 0.4 to 0.6, the above W LiPF6 For example, it can be about 12 wt% to 16 wt%, preferably 13 wt% to 16 wt%. The WLiPF6 If the value is somewhat small, the electrolyte viscosity is low and the electrolyte has high fluidity, so it is easy to inject the electrolyte into a large-capacity battery, but the lithium ion conductivity decreases, which may result in deterioration of cycle characteristics, etc. On the other hand, the above W LiPF6 If the value is somewhat high, the electrolyte viscosity increases and the fluidity decreases, which may result in deterioration of electrolyte wetting, resulting in a decrease in initial performance, and a decrease in high-temperature durability and cycle characteristics.

[0065]

[0066] In the above equation (1), W EC The content of ethylene carbonate is expressed as a percentage (%) with respect to the total weight of the electrolyte during the manufacture of the electrolyte, and the viscosity of the electrolyte can be controlled according to the content of the ethylene carbonate.

[0067] The above ethylene carbonate is an organic solvent with excellent compatibility with carbon materials and has been primarily used as an electrolyte solvent for lithium secondary batteries. However, if the electrolyte contains a relatively large amount of ethylene carbonate, the decomposition of ethylene carbonate during charge and discharge may 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, so if it contains a relatively large amount, low-temperature characteristics are reduced, conductivity is low, high-power characteristics are reduced, and electrolyte viscosity increases. Conversely, if the electrolyte contains a relatively small amount of ethylene carbonate, electrical conductivity may be reduced, which may deteriorate thermal stability and life performance.

[0068] When the form factor ratio of the lithium secondary battery of the present invention is 0.4 to 0.6, the ethylene carbonate content (W) in the electrolyte EC ) is preferably about 13 wt% to 25 wt%, preferably 15 wt% to 20 wt%. The W ECWhen the value satisfies the above range, the optimal electrolyte impregnation conditions for a large-capacity cylindrical secondary battery can be established.

[0069]

[0070] Meanwhile, the high-temperature durability and cycle characteristics of lithium secondary batteries are closely related to the viscosity of the electrolyte. That is, when a high-viscosity electrolyte is injected into a large-capacity cylindrical lithium secondary battery having a form factor ratio of 0.4 or more, preferably 0.4 to 0.6 as described above, the impregnation (wettability) of the electrode assembly is reduced, so that the charge / discharge performance of the lithium secondary battery is significantly reduced or charging / discharging is impossible. In contrast, when a low-viscosity electrolyte is injected into a large-capacity battery, the impregnation (wettability) of the electrode assembly is improved, but there is a problem that the charge / discharge performance of the lithium secondary battery is significantly reduced due to the low lithium salt concentration in the electrolyte.

[0071] In the present invention, by satisfying specific conditions such as the above formula (1) in terms of the electrolyte composition and amount depending on the dimensions of the battery cell, it is possible to establish optimal electrolyte impregnation conditions suitable for a large-capacity cylindrical lithium secondary battery, thereby manufacturing a lithium secondary battery capable of exhibiting excellent high-temperature durability and cycle characteristics. That is, by injecting an appropriate amount of an electrolyte containing an optimal lithium salt (LiPF6) and EC into the limited internal space of a cylindrical cell, the internal pressure of the cell is controlled while improving the wetting of the electrode assembly with respect to the electrolyte, thereby suppressing an increase in resistance and significantly improving the high-temperature cycle characteristics.

[0072]

[0073] Meanwhile, Fig. 1 illustrates a pre-winding laminated structure of an electrode assembly according to the present invention, Fig. 2 illustrates a cross-sectional structure of an electrode plate (positive electrode or negative electrode) according to the present invention, and Fig. 3 illustrates a structure of an electrode assembly according to one embodiment of the present invention. In addition, Figs. 4 and 5 illustrate cross-sectional views of a cylindrical battery having a tab-less structure according to one embodiment of the present invention. Hereinafter, with reference to the drawings, each component of the cylindrical battery having a tab-less structure according to the present invention will be described in more detail.

[0074]

[0075] [Electrode assembly]

[0076] Referring to FIGS. 1 and 2, the electrode assembly (A) of the present invention can be manufactured by winding a laminate formed by sequentially stacking a separator (12), an anode (10), a separator (12), and a cathode (11) at least once in one direction (X).

[0077] At this time, the positive electrode (10) and negative electrode (11) have a structure in which an active material layer (21) is formed on a long sheet-shaped current collector (20), and may include a non-conductive portion (22) in which an active material layer (21) is not formed in some area of ​​the current collector (20).

[0078] By using the positive electrode (10) and negative electrode (11) including the non-conductive portion (22) as described above, a battery having a tab-less structure in which at least a portion of the non-conductive portion of the positive electrode (10) and negative electrode (11) defines the electrode tab can be implemented without providing a separate electrode tab.

[0079] Specifically, the non-conductive portion (22) can be formed long along the winding direction (X) at one end of the current collector (20), and a current collector plate can be combined with each of the non-conductive portion of the positive electrode and the non-conductive portion of the negative electrode, and the current collector plate can be connected to an electrode terminal, thereby implementing a battery with a tab-less structure.

[0080] For example, a battery having a tab-less structure can be manufactured by the following method. First, a separator, a positive electrode, a separator, and a negative electrode are sequentially stacked so that the non-coated portions (22) of the positive electrode (10) and the negative electrode (11) are positioned in opposite directions, and then the separator is wound in one direction to manufacture a jelly-roll type electrode assembly. Then, the non-coated portions (22) of the positive and negative electrodes are bent toward the winding center (C), and then a current collector plate is welded to the non-coated portion of the positive electrode and the non-coated portion of the negative electrode to join them, and the current collector plate is connected to the electrode terminal, thereby manufacturing a battery having a tab-less structure. Meanwhile, the current collector plate has a larger cross-sectional area than the strip-type electrode tab, and since the resistance is inversely proportional to the cross-sectional area of ​​the path through which the current flows, when a secondary battery is formed with the above structure, the cell resistance can be significantly reduced.

[0081] Meanwhile, the non-conductive portions of the positive and negative electrodes may be processed into a plurality of independently bendable segments, and at least some of the plurality of segments may be bent toward the winding center (C) of the electrode assembly.

[0082] The above segments can be formed by processing the positive and negative current collectors through a metal foil cutting process such as laser notching, ultrasonic cutting, or punching.

[0083] When the non-conductive portions of the positive and negative electrodes are processed in the form of multiple segments, the stress applied to the non-conductive portion during bending can be reduced, thereby preventing deformation or damage to the non-conductive portion, and the welding characteristics with the current collector plate can be improved.

[0084] The collector plate and the non-coated portion are typically joined by welding. To improve welding properties, strong pressure must be applied to the welding area of ​​the non-coated portion to fold it as flat as possible. However, during this bending process, the non-coated portion may become irregularly distorted and deformed, and the deformed portion may contact the electrode of the opposite polarity, causing an internal short circuit or causing micro-cracks in the non-coated portion. However, if the non-coated portions of the positive and negative electrodes are processed into multiple independently bendable segments, the stress applied to the non-coated portion during bending can be alleviated, thereby minimizing deformation and damage to the non-coated portion.

[0085] In addition, when the non-conductive portion is processed in the form of segments as described above, overlap occurs between the plurality of segments during bending, which increases the welding strength with the current collector plate, and when using the latest technology such as laser welding, it is possible to prevent the problem of the laser penetrating into the electrode assembly and melting the separator or active material. Preferably, at least some of the plurality of folded segments may overlap on the upper and lower sides of the electrode assembly, and the current collector plate may be bonded on the plurality of overlapped segments.

[0086] Meanwhile, the electrode assembly according to the present invention may be formed with a structure in which an insulating layer (24) is additionally formed on the positive electrode (10), as illustrated in FIG. 3. Specifically, the insulating layer (24) may be formed to cover a portion of the positive electrode active material layer and a portion of the non-conductive portion in a direction parallel to the winding direction of the electrode assembly.

[0087] In the case of a battery having a tab-less structure that uses the non-conductive portion (22c) of the positive electrode (10) and the non-conductive portion (22a) of the negative electrode (11) as electrode tabs, an electrode assembly is formed so 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 folded and then combined with a current collecting plate. However, when the positive electrode (10) or negative electrode (11) is folded as described above, the current collector of the positive electrode (10) or negative electrode (11) is positioned close to an electrode of the opposite polarity beyond the separator, which may cause the positive electrode and negative electrode to come into electrical contact, thereby causing an internal short circuit. However, as shown in Fig. 5, when an insulating layer (24) covering the positive electrode active material layer and a portion of the non-conductive portion is formed, the positive electrode (10) and the negative electrode (11) can be prevented from electrically contacting each other by the insulating layer (24), thereby preventing a short circuit from occurring inside the battery.

[0088] Preferably, the insulating layer (24) may be provided on at least one side of the positive electrode (10) current collector, and preferably, may be provided on both sides of the positive electrode (10).

[0089] In addition, the insulating layer (24) may be formed in an area of ​​the positive electrode (10) that is likely to face the active material layer (21a) of the negative electrode (11). For example, on the surface of the non-coated portion (22c) of the positive electrode (10) that faces the negative electrode (11) after being folded, the insulating layer (24) may be formed to extend to the end of the non-coated portion (22c). However, in the case of the surface opposite to the surface that faces the negative electrode (11) after being folded, it is preferable that the insulating layer (24) be formed only on a part of the non-coated portion (22c), for example, up to the bending point of the non-coated portion (22c). This is because, if the insulating layer (24) is formed on the entire area of ​​the non-coated portion on the surface opposite to the surface that faces the negative electrode (11), electrical contact with the current collecting plate is impossible, making it impossible to function as an electrode tab.

[0090] Meanwhile, the insulating layer (24) can be attached to the anode while ensuring insulating performance, and its material or composition is not particularly limited. For example, the insulating layer may be an insulating coating layer or an insulating tape, and the insulating coating layer may include an organic binder and inorganic particles. In this case, the organic binder may be, for example, styrene-butadiene rubber (SBR), and the inorganic particles may be, but are not limited to, alumina oxide.

[0091] Meanwhile, the diameter (diameter) of the electrode assembly core of the present invention may be 5 mm or more, specifically, 5 mm to 8 mm. When the diameter of the electrode assembly core satisfies the above range, the defect rate can be suppressed during the winding process for manufacturing a jelly-roll electrode assembly, and sufficient space for electrolyte injection can be secured inside the cylindrical secondary battery. Meanwhile, when the diameter (diameter) of the electrode assembly core is less than 5 mm, the pressure inside the cell increases, which may cause issues such as venting. Conversely, when the diameter (diameter) of the electrode assembly core exceeds 8 mm, the energy density per cell volume decreases, and the wettability with respect to the electrolyte deteriorates, which may cause deterioration of cell performance. In particular, in the case of a large cylindrical battery having a form factor of 0.4 or more, by injecting an electrolyte having an appropriate level of viscosity, the electrolyte impregnation property for the electrode assembly can be improved, thereby bringing about improvement in cell performance.

[0092] Meanwhile, the overall diameter of the electrode assembly may have a typical diameter suitable for a large cylindrical battery having a form factor of 0.4 or greater.

[0093]

[0094] Next, each component of the electrode assembly of the present invention will be described in more detail.

[0095] anode

[0096] The above positive electrode can be manufactured by applying positive electrode slurry to one or both sides of a long sheet-shaped positive electrode collector, removing the solvent of the positive electrode slurry through a drying process, and then rolling. Meanwhile, a positive electrode including a non-coated region can be manufactured by not applying the positive electrode slurry to some areas of the positive electrode collector, for example, one end of the positive electrode collector, during the application of the positive electrode slurry.

[0097] Meanwhile, as the positive electrode current collector, various positive electrode current collectors used in the relevant technical field can be used. For example, the positive electrode current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0098] Additionally, the positive electrode slurry can be manufactured by dispersing the positive electrode active material in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water.

[0099] The above positive electrode active material may be a positive electrode active material generally used in the relevant technical field, but preferably, a lithium transition metal oxide containing Ni and Co may be used, and specifically, it may include a lithium transition metal oxide satisfying the following formula (2).

[0100] Equation (2):

[0101] 18 ≤ X Ni / X Co ≤ 48

[0102] In the above equation (2), X Ni is the molar percentage of Ni among the total metals excluding lithium in the above lithium transition metal oxide, and X Co is the molar percentage of Co among the total metals excluding lithium in the above lithium transition metal oxide.

[0103] When the composition ratio of Ni and Co in the lithium transition metal oxide represented by the above formula (2) is less than 18, the side reaction with the electrolyte increases, causing an increase in the interface resistance. In contrast, when the composition ratio of Ni and Co satisfies 18 to 48, the structural stability of the positive electrode active material is improved, and the side reaction with the electrolyte can be effectively prevented as the oxidation reaction is suppressed. Specifically, it is more preferable that the composition ratio of Ni and Co in the lithium transition metal oxide is 40 or less, or 35 or less.

[0104] Preferably, the lithium transition metal oxide can be represented by the following [chemical formula 1].

[0105] [Chemical Formula 1]

[0106] Li a Ni b Co c M 1 d M 2 e O2

[0107] In the above chemical formula 1, M 1 It may be Mn, Al or a combination thereof, preferably Mn or Mn and Al.

[0108] Above M 2 is at least one selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta and Nb, preferably at least one selected from the group consisting of Zr, Y, Mg, and Ti, and more preferably Zr, Y or a combination thereof. M 2Although elements are not essential, when included in appropriate amounts, they can promote grain growth during firing or play a role in improving crystal structure stability.

[0109] The above a represents the molar ratio of lithium in the lithium nickel-based oxide, and may be 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 stably formed.

[0110] The above b represents the molar ratio of nickel among all metals excluding lithium in the lithium nickel oxide, and is 0.85. <b<1, 0.87≤b<1, 또는 0.9≤b<1일 수 있다. 니켈의 몰비가 상기 범위를 만족할 때, 높은 에너지 밀도를 나타내어 고용량 구현이 가능하다.

[0111] The above c represents the molar ratio of cobalt among all metals excluding lithium in the lithium nickel oxide, and is 0. <c<0.06, 또는 0.01≤c≤0.05일 수 있다. 코발트의 몰비가 상기 범위를 만족할 때, 양호한 저항 특성 및 출력 특성을 구현할 수 있다.

[0112] The above d is M of all metals excluding lithium in lithium nickel oxide. 1 It represents the molar ratio of elements, 0 <d<0.15, 0<d<0.14, 또는 0.01≤d≤0.12일 수 있다. M 1 When the molar ratio of the elements satisfies the above range, the structural stability of the positive electrode active material is excellent.

[0113] The above e is M of all metals except lithium in lithium nickel oxide. 2 It represents the molar ratio of elements, and can be 0≤e≤0.1 or 0≤e≤0.05.

[0114] Specifically, the positive electrode active material of the present invention is Li(Ni 0.90 Mn 0.05 Co 0.05 )O2, Li(Ni) 0.94 Co 0.04 Mn 0.02 )O 2, 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 )It could be O2.

[0115] Meanwhile, the positive electrode slurry may optionally further include at least one of a conductive material and a binder.

[0116] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples 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 black, carbon fiber, and carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may typically be included in an amount of 1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on the total weight of the positive electrode active material layer.

[0117] The above binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector, and specific examples thereof include a fluororesin binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); a rubber binder including styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; a cellulose binder including carboxyl methyl cellulose (CMC), starch, hydroxy propyl cellulose, and regenerated cellulose; a polyalcohol binder including polyvinyl alcohol; a polyolefin binder including polyethylene and polypropylene; a polyimide binder; and a polyester binder. And silane binders, etc. can be mentioned, and one of these can be used alone or a mixture of two or more can be used. The binder can be included in an amount of 1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on the total weight of the positive electrode active material layer.

[0118]

[0119] cathode

[0120] The above negative electrode can be manufactured by applying negative electrode slurry to one or both sides of a long sheet-shaped negative electrode collector, removing the solvent of the negative electrode slurry through a drying process, and then rolling. Meanwhile, a negative electrode including a non-coated region can be manufactured by not applying the negative electrode slurry to some areas of the negative electrode collector, for example, one end of the negative electrode collector, during the application of the negative electrode slurry.

[0121] Meanwhile, as the negative electrode current collector, negative electrode current collectors generally used in the relevant technical field can be used, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. The negative electrode current collector can typically have a thickness of 3 to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0122] Additionally, the negative electrode slurry can be manufactured by dispersing the negative electrode active material in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc.

[0123] As the above negative electrode active material, a carbon-based negative electrode active material used in the relevant industry can be used, and further, a silicon-based negative electrode active material can be mixed with the carbon-based negative electrode active material and used.

[0124] The above carbon-based active material may be a variety of carbon-based materials used in the art, for example, graphite-based materials such as natural graphite, artificial graphite, and Kish graphite; pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes, soft carbon, hard carbon, etc. The shape of the carbon-based material is not particularly limited, and materials of various shapes such as amorphous, plate-like, flaky, spherical, or fibrous may be used.

[0125] In addition, the silicon-based negative electrode active material may be, for example, silicon (Si), silicon carbide (SiC), silicon chloride, and silicon oxide (SiO). x , here 0 <x<2), Si-Y 합금(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님)로 이루어진 군으로부터 선택된 1종 이상을 포함할 수 있다. 상기 원소 Y로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db (dubnium), Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, 및 이들의 조합으로 이루어진 군에서 선택될 수 있다.

[0126] Meanwhile, 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.

[0127] When the mixing ratio of the above carbon-based negative electrode active material and the silicon-based negative electrode active material satisfies the above range, the capacity characteristics can be improved while the volume expansion of the silicon-based compound is suppressed, thereby ensuring excellent cycle performance. When the silicon (Si)-based compound is too small, it is difficult to increase the energy density, making it difficult to increase the capacity of the battery, and when it is too large, the degree of volume expansion of the negative electrode can be large, which is not desirable.

[0128] Meanwhile, the cathode slurry may optionally additionally include at least one of a conductive material and a binder.

[0129] The conductive material is used to provide conductivity to the negative electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples 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 black, carbon fiber, and carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may typically be included in an amount of 1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on the total weight of the negative electrode active material layer.

[0130] The above binder serves to improve adhesion between negative electrode active material particles and adhesiveness between the negative electrode active material and the negative electrode current collector. Specific examples include a fluororesin binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); a rubber binder including styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; a cellulose binder including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyalcohol binder including polyvinyl alcohol; a polyolefin binder including polyethylene and polypropylene; a polyimide binder; and a polyester binder. And silane binders, etc. can be mentioned, and one of these can be used alone or a mixture of two or more can be used. The binder can be included in an amount of 1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on the total weight of the negative electrode active material layer.

[0131]

[0132] membrane

[0133] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions. Specifically, the separator may be a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength.

[0134]

[0135] [Cylindrical lithium secondary battery]

[0136] Next, a cylindrical lithium secondary battery according to the present invention will be described.

[0137] A cylindrical lithium secondary battery according to the present invention comprises an electrode assembly formed by winding a positive electrode and a negative electrode including a non-conductive portion, an electrolyte, a battery case in which the electrode assembly and the electrolyte are stored, and a sealing body for sealing an open end of the battery case. In addition, a tab-less structure can be implemented in which at least a portion of the non-conductive portion of the positive electrode or the non-conductive portion of the negative electrode is defined as an electrode tab.

[0138]

[0139] Preferably, the cylindrical lithium secondary battery according to the present invention may be a large cylindrical battery having a form factor ratio (defined as the ratio of the diameter (T) to the height (H) of the cylindrical battery, i.e., the diameter divided by the height) of 0.4 or more, preferably 0.4 to 0.6. Here, the form factor refers to a value indicating the diameter and height of the cylindrical battery.

[0140] The cylindrical battery according to the present invention may be, for example, a 46110 cell (diameter 46 mm, height 110 mm, form factor ratio 0.418), a 48110 cell (diameter 48 mm, height 110 mm, form factor ratio 0.436), a 4880 cell (diameter 48 mm, height 80 mm, form factor ratio 0.600), or a 4680 cell (diameter 46 mm, height 80 mm, form factor ratio 0.575). In the numerical value indicating the form factor, the first two numbers indicate the diameter of the cell, and the next two or three numbers indicate the height of the cell.

[0141] Meanwhile, the cylindrical battery according to the present invention may preferably be a battery having a tab-less structure that does not include electrode tabs, but is not limited thereto.

[0142] The battery of the tab-less structure may have, for example, a structure in which the positive electrode and the negative electrode each include a non-conductive portion on which an active material layer is not formed, the non-conductive portion of the positive electrode and the non-conductive portion of the negative electrode are respectively positioned at the top and bottom of the electrode assembly, a current collecting plate is bonded to the non-conductive portion of the positive electrode and the non-conductive portion of the negative electrode, and the current collecting plate is connected to an electrode terminal.

[0143] Figures 4 and 5 illustrate cross-sectional views of a cylindrical battery having a tab-less structure according to one embodiment of the present invention. Hereinafter, a cylindrical battery according to one embodiment of the present invention will be described with reference to Figures 4 and 5. However, Figures 4 and 5 merely illustrate one embodiment of the present invention, and the structure of the cylindrical battery of the present invention is not limited to the scope disclosed in Figures 4 and 5.

[0144] A cylindrical battery (140) according to one embodiment of the present invention includes the above-described jelly-roll type electrode assembly (141), a battery case (142) in which the electrode assembly (141) and an electrolyte (not shown) are stored, and a sealing body (143) that seals the open end of the battery case (142).

[0145] At this time, the positive and negative electrodes of the electrode assembly may each include a non-conductive portion on which an active material layer is not formed, and may be laminated and wound so that the non-conductive portion of the positive electrode and the non-conductive portion of the negative electrode are positioned at the top and bottom of the electrode assembly, respectively. Since the electrode assembly has been described above, only the remaining components excluding the electrode assembly will be described below.

[0146] The battery case (142) is a cylindrical container with an opening formed at the top, and is made of a conductive metal material such as aluminum or steel. The battery case accommodates an electrode assembly (141) in an inner space through the upper opening, and also accommodates an electrolyte (not shown).

[0147] Meanwhile, it is preferable that the cylindrical battery (140) of the present invention does not include a current interruption device (CID).

[0148]

[0149] electrolyte

[0150] Meanwhile, 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.

[0151] In addition, the electrolyte of the present invention may additionally include at least one organic solvent among a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, and a cyclic ester-based organic solvent, as needed.

[0152] The above cyclic carbonate-based organic solvent is a high-viscosity organic solvent, and may 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-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0153] In addition, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and representative examples thereof include 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 specifically, at least one of ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) may be included.

[0154] Specific examples of the linear ester organic solvent include 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.

[0155] The above cyclic ester organic solvent may include at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0156]

[0157] Meanwhile, in addition to the electrolyte components, the electrolyte may additionally include other additives for the purpose of improving the life characteristics of the battery, suppressing battery capacity reduction, and improving the discharge capacity of the battery.

[0158] These other additives may include, as representative examples, at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds different from the lithium salt included in the electrolyte.

[0159] Specifically, the other additives include vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), 1,4-butane sultone, ethene 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), tetraphenylborate, lithium oxalyldifluoroborate, succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, One or more compounds selected from the group consisting of 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(trifluoromethane sulfonyl)imide, LiTFSI), LiPO2F2, LiODFB, LiBOB (lithium bisoxalatoborate (LiB(C2O4)2) and LiBF4) may be mentioned.

[0160] The above-mentioned other additives may be included in an amount of 0.01 to 20 wt% based on the total weight of the electrolyte, and preferably 0.05 to 5.0 wt%. If the content of the above-mentioned other additives is less than 0.01 wt%, the effects of improving the low-temperature output of the battery and the high-temperature storage characteristics and high-temperature life characteristics are minimal, and if the content of the above-mentioned other additives exceeds 20 wt%, there is a possibility that side reactions may occur excessively in the electrolyte during charge and discharge of the battery. In particular, when the above-mentioned SEI film forming additives are added in excessive amounts, they may not be sufficiently decomposed at high temperatures and may remain unreacted or precipitated in the electrolyte at room temperature. Accordingly, side reactions that reduce the life or resistance characteristics of the secondary battery may occur.

[0161]

[0162] Meanwhile, in FIG. 4, the battery case (142) is electrically connected to the negative electrode's non-conductive portion (146b), and functions as a negative terminal that contacts an external power source and transmits current applied from the external power source to the negative electrode.

[0163] At this time, the battery case (142) is a cylindrical container with an opening formed at the top, and is made of a conductive metal material such as aluminum or steel. The battery case accommodates an electrode assembly (141) in the inner space through the upper opening, and also accommodates an electrolyte (not shown).

[0164] If necessary, a beading portion (147) and a crimping portion (148) may be provided on the upper end of the battery case (142). The beading portion (147) may be formed by pressing the outer circumference of the battery case (142) to a distance of D1. The beading portion (147) may prevent the electrode assembly (141) accommodated inside the battery case (142) from coming out through the upper opening of the battery case (142), and may function as a support portion on which the sealing body (143) is secured.

[0165] The above crimping portion (148) can be formed on the upper portion of the beading portion (147), and has an extended and bent shape to surround the outer surface of the cap plate (143a) placed on the beading portion (147) and a portion of the upper surface of the cap plate (143a).

[0166]

[0167] Next, the sealing member (143) is for sealing the open end of the battery case (142), and includes a cap plate (143a), a first gasket (143b) that provides airtightness between the cap plate (143a) and the battery case (142) and has insulation, and may further include a connecting plate (143c) that is electrically and mechanically coupled to the cap plate (143a), if necessary. The cap plate (143a) is pressed onto a beading portion (147) formed on the battery case (142), and may be fixed by a crimping portion (148).

[0168] The cap plate (143a) is a component made of a conductive metal material and covers the upper opening of the battery case (142). The cap plate (143a) is electrically connected to the positive electrode of the electrode assembly (141) and is electrically insulated from the battery case (142) via a first gasket (143b). Therefore, the cap plate (143a) can function as a positive electrode terminal of a cylindrical secondary battery. The cap plate (143a) can have a protrusion (143d) formed to protrude upward from its center portion C, and the protrusion (143d) can come into contact with an external power source to allow current to be applied from the external power source.

[0169] A first gasket (143b) may be interposed between the cap plate (143a) and the crimping portion (148) to ensure the airtightness of the battery case (142) and to provide electrical insulation between the battery case (142) and the cap plate (143a).

[0170] Meanwhile, the cylindrical battery (140) according to the present invention may further include a current collecting plate (144, 145) as needed. The current collecting plate is coupled to the non-conductive portion (146a) of the positive electrode and the non-conductive portion (146b) of the negative electrode, and is connected to the electrode terminals (i.e., the positive terminal and the negative terminal).

[0171] Specifically, a cylindrical battery (140) according to the present invention may include a first current collecting plate (144) coupled to the upper portion of an electrode assembly (141) and a second current collecting plate (145) coupled to the lower portion of the electrode assembly (141).

[0172] It may further include a first collector plate (144) and / or a second collector plate (145).

[0173] The first current collecting plate (144) is coupled to the upper portion of the electrode assembly (141). The first current collecting plate (144) is made of a conductive metal material such as aluminum, copper, nickel, etc., and is electrically connected to the non-conductive portion (146a) of the positive electrode. A lead (149) may be coupled to the first current collecting plate (144). The lead (149) may extend upward from the electrode assembly (141) and be coupled to the connection plate (143c) or may be directly coupled to the lower surface of the cap plate (143a). The coupling of the lead (149) to other components may be achieved through welding. Preferably, the first current collecting plate (144) may be formed integrally with the lead (149). In this case, the lead (149) may have a long plate shape extending outward from the center of the first current collecting plate (144).

[0174] Meanwhile, the first collector plate (144) is coupled to the end of the non-conductive portion (146a) of the anode, and the coupling can be achieved by, for example, laser welding, resistance welding, ultrasonic welding, soldering, or the like.

[0175] The second current collecting plate (145) is coupled to the lower portion of the electrode assembly (141). The second current collecting plate (145) is made of a conductive metal material such as aluminum, copper, nickel, etc., and is electrically connected to the non-conductive portion (146b) of the negative electrode. One side of the second current collecting plate (145) can be coupled to the non-conductive portion (146b) of the negative electrode, and the opposite side can be coupled to the inner bottom surface of the battery case (142). At this time, the coupling can be performed by a method such as laser welding, resistance welding, ultrasonic welding, or soldering.

[0176] Meanwhile, the cylindrical battery (140) according to the present invention may further include an insulator (146), if necessary. The insulator (146) may be arranged to cover the upper surface of the first current collecting plate (144). By covering the first current collecting plate (144) with the insulator (146), direct contact between the first current collecting plate (144) and the inner surface of the battery case (142) can be prevented.

[0177] The insulator (146) has a lead hole (151) through which a lead (149) extending upward from the first collector plate (144) can be drawn out. The lead (149) is drawn upward through the lead hole (151) and is coupled to the lower surface of the connecting plate (143c) or the lower surface of the cap plate (143a).

[0178] The insulator (146) may be made of a polymer resin material having insulating properties, such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

[0179] Meanwhile, the cylindrical battery (140) according to the present invention may further include a venting portion (152) formed on the lower surface of the battery case (142), if necessary. The venting portion (152) corresponds to a region of the lower surface of the battery case (142) that has a thinner thickness than the surrounding region. Since the venting portion (152) is thin, it is structurally weaker than the surrounding region. Therefore, when the pressure inside the cylindrical battery (140) increases above a certain level, the venting portion (152) ruptures, allowing the gas inside the battery case (152) to be discharged to the outside, thereby preventing the battery from exploding.

[0180]

[0181] FIG. 5 illustrates a cross-sectional view of a cylindrical battery with a tab-less structure according to another embodiment of the present invention. Hereinafter, a cylindrical battery according to another embodiment of the present invention will be described with reference to FIG. 5. However, FIG. 5 merely illustrates one embodiment of the present invention, and the structure of the cylindrical battery according to the present invention is not limited to the scope disclosed in FIG. 5.

[0182] Referring to FIG. 5, a cylindrical battery (170) according to another embodiment of the present invention has a different structure of a battery case and a sealing body compared to the cylindrical battery (140) illustrated in FIG. 3, and the configuration of the electrode assembly and electrolyte are substantially the same.

[0183] Specifically, the cylindrical battery (170) includes a battery case (171) through which a rivet terminal (172) is installed. The rivet terminal (172) is installed in a partially closed closed surface (upper surface in the drawing) at one end of the battery case (171). The rivet terminal (172) is riveted to a through hole (first opening at the first end) of the battery case (171) while an insulating second gasket (173) is interposed therebetween. The rivet terminal (172) is exposed to the outside in a direction opposite to the gravity direction.

[0184] The rivet terminal (172) includes a terminal exposure portion (172a) and a terminal insertion portion (172b). The terminal exposure portion (172a) is exposed to the outside of the closed surface of the battery case (171). The terminal exposure portion (172a) may be located approximately at the center of the partially closed surface of the battery case (171). The maximum diameter of the terminal exposure portion (172a) may be formed to be larger than the maximum diameter of the through hole formed in the battery case (171). The terminal insertion portion (172b) may penetrate approximately at the center of the closed surface of the battery case (171) and be electrically connected to the non-coated portion (146a) of the positive electrode. The terminal insertion portion (172b) may be riveted onto the inner surface of the battery case (171). That is, the end of the terminal insertion portion (172b) may have a shape that is bent toward the inner surface of the battery case (171). The maximum diameter of the end of the terminal insertion portion (172b) may be larger than the maximum diameter of the through hole of the battery case (171).

[0185] The lower surface of the terminal insertion portion (172b) can be welded to the first current collecting plate (144) connected to the non-polarized portion (146a) of the positive electrode. An insulating cap (174) made of an insulating material can be interposed between the first current collecting plate (144) and the inner surface of the battery case (171). The insulating cap (174) covers the upper portion of the first current collecting plate (144) and the upper edge portion of the electrode assembly (141). This can prevent the outer non-polarized portion (B3) of the electrode assembly (141) from coming into contact with the inner surface of the battery case (171) having a different polarity, thereby causing a short circuit. The terminal insertion portion (172b) of the rivet terminal (172) can be welded to the first current collecting plate (144) by penetrating the insulating cap (174).

[0186] The second gasket (173) is interposed between the battery case (171) and the rivet terminal (172) to prevent the battery case (171) and the rivet terminal (172) having opposite polarities from making electrical contact. This allows the upper surface of the battery case (171) having a roughly flat shape to function as the positive terminal of the cylindrical battery (170).

[0187] The second gasket (173) includes a gasket exposure portion (173a) and a gasket insertion portion (173b). The gasket exposure portion (173a) is interposed between the terminal exposure portion (172a) of the rivet terminal (172) and the battery case (171). The gasket insertion portion (173b) is interposed between the terminal insertion portion (172b) of the rivet terminal (172) and the battery case (171). The gasket insertion portion (173b) can be deformed together with the terminal insertion portion (172b) when riveting and can be brought into close contact with the inner surface of the battery case (171). The second gasket (173) can be made of, for example, an insulating polymer resin.

[0188] The gasket exposure portion (173a) of the second gasket (173) may have an extended shape to cover the outer surface of the terminal exposure portion (172a) of the rivet terminal (172). When the second gasket (173) covers the outer surface of the rivet terminal (172), a short circuit can be prevented from occurring during the process of connecting an electrical connection component such as a bus bar to the upper surface of the battery case (171) and / or the rivet terminal (172). Although not shown in the drawing, the gasket exposure portion (173a) may have an extended shape to cover not only the outer surface of the terminal exposure portion (172a) but also a portion of the upper surface.

[0189] In the case where the second gasket (173) is made of a polymer resin, the second gasket (173) can be joined to the battery case (171) and the rivet terminal (172) by heat fusion. In this case, the sealing properties at the joining interface between the second gasket (173) and the rivet terminal (172) and at the joining interface between the second gasket (173) and the battery case (171) can be strengthened. Meanwhile, in the case where the gasket exposure portion (173a) of the second gasket (173) has a form that extends to the upper surface of the terminal exposure portion (172a), the rivet terminal (172) can be integrally joined to the second gasket (173) by insert injection.

[0190] Among the upper surfaces of the battery case (171), the remaining area (175) excluding the area occupied by the rivet terminal (172) and the second gasket (173) corresponds to a negative terminal having a polarity opposite to that of the rivet terminal (172).

[0191] The second collector plate (176) is coupled to the lower portion of the electrode assembly (141). The second collector plate (176) is made of a conductive metal material such as aluminum, steel, copper, or nickel, and is electrically connected to the non-conductive portion (146b) of the negative electrode.

[0192] Preferably, the second current collecting plate (176) is electrically connected to the battery case (171). To this end, at least a portion of the edge portion of the second current collecting plate (176) may be interposed 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 collecting plate (176) may be fixed to the beading portion (180) formed at the bottom of the battery case (171) by welding while being supported by the lower surface of the beading portion (180). In a variation, at least a portion of the edge portion of the second current collecting plate (176) may be directly welded to the inner wall surface of the battery case (171).

[0193] The second collector plate (176) may have a plurality of protrusions (not shown) radially formed on a surface facing the non-conductive portion (146b). When the protrusions are formed, the second collector plate (176) can be pressed to press the protrusions into the non-conductive portion (146b).

[0194] Preferably, the ends of the second collector plate (176) and the non-conductive portion (146b) can be joined by welding, for example, laser welding.

[0195] A sealing member (178) for sealing the lower open end of the battery case (171) includes a cap plate (178a) and a first gasket (178b). The first gasket (178b) electrically separates the cap plate (178a) and the battery case (171). A crimping member (181) secures the edge of the cap plate (178a) and the first gasket (178b) together. A vent member (179) is provided in the cap plate (178a). The configuration of the vent member (179) is substantially the same as in the above-described embodiment.

[0196] Preferably, the cap plate (178a) is made of a conductive metal material. However, since a first gasket (178b) is interposed between the cap plate (178a) and the battery case (171), the cap plate (178a) does not have electrical polarity. The sealing body (178) seals the open end at the bottom of the battery case (171) and functions to discharge gas when the internal pressure of the battery cell (170) increases above a critical value.

[0197] Preferably, the rivet terminal (172) electrically connected to the non-conductive portion (146a) of the positive electrode is used as the positive terminal. In addition, the portion (175) of the upper surface of the battery case (171) electrically connected to the non-conductive portion (146b) of the negative electrode through the second current collecting plate (176), excluding the rivet terminal (172), is used as the negative terminal. In this way, when the two electrode terminals are located at the upper part of the cylindrical battery, electrical connection parts such as bus bars are used.

[0198] (170) can be placed only on one side. This can lead to simplification of the battery pack structure and improvement of energy density. In addition, since the portion (175) used as the negative terminal has a roughly flat shape, a sufficient bonding area can be secured for bonding electrical connection components such as bus bars. Accordingly, the cylindrical battery (170) can reduce the resistance at the bonding site of the electrical connection components to a desirable level.

[0199] When a cylindrical lithium secondary battery is formed with a tab-less structure as described above, the current concentration is less than that of a conventional battery having electrode tabs, so heat generation inside the battery can be effectively reduced, and thus the thermal safety of the battery can be improved.

[0200]

[0201] The cylindrical lithium secondary battery of the present invention as described above can be used to manufacture a battery pack. FIG. 6 schematically illustrates the configuration of a battery pack according to an embodiment of the present invention. Referring to FIG. 6, a battery pack (3) according to an embodiment of the present invention includes an assembly of cylindrical secondary batteries (1) electrically connected thereto and a pack housing (2) accommodating the same. The cylindrical secondary battery (1) is a battery cell according to the embodiment described above. In the drawing, for the convenience of illustration, components such as a bus bar, a cooling unit, and an external terminal for electrical connection of the cylindrical secondary batteries (1) are omitted.

[0202] The above battery pack (3) can be mounted on a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle includes a four-wheel vehicle or a two-wheel vehicle.

[0203]

[0204] Hereinafter, the present invention will be described in more detail through specific examples.

[0205] Example 1.

[0206] (Electrolyte manufacturing)

[0207] An electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 in a non-aqueous organic solvent to have a LiPF6 concentration of 1.3 M (ethylene carbonate content: 19.17 wt% / LiPF6 content: 15.41 wt%) (see Table 1 below).

[0208]

[0209] (Secondary battery manufacturing)

[0210] Average particle diameter D 50 This positive electrode active material (Li(Ni)) has a unimodal particle size distribution of 3 ㎛ and is in the form of a single particle. 0.90 Mn 0.03 Co 0.05 Al 0.02 )O2) and Carbon nanotubes and PVDF binder were added and mixed in a weight ratio of 97.8:0.6:1.6 in N-methylpyrrolidone to prepare a cathode slurry. The cathode slurry was applied to one side of an aluminum current collector sheet, dried at 120°C, and then rolled to prepare a cathode plate.

[0211] A negative electrode slurry was prepared by adding and mixing a negative electrode active material (graphite and SiO = 95:5 weight ratio), a conductive agent (super C), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) in a weight ratio of 96:2:1.5:0.5 to water. The negative electrode slurry was applied to one surface of a copper current collector sheet, dried at 150°C, and then rolled to prepare a negative electrode plate.

[0212] A separator was interposed between the positive and negative plates manufactured as described above, and the separator / positive plate / separator / negative plate were stacked in that order, and then wound to manufacture an electrode assembly (core diameter: 7 mm). The electrode assembly manufactured as described above was inserted into a cylindrical battery can (diameter: 46 mm / height: 80 mm), and the electrolyte (38 g) was injected to manufacture a 4680 cell (form factor ratio: 0.575).

[0213]

[0214] Example 2.

[0215] (Secondary battery manufacturing)

[0216] An electrolyte and a 4680 cell (form factor ratio: 0.575) containing the same were manufactured in the same manner as in Example 1, except that the electrolyte (31 g) of Example 1 was injected.

[0217]

[0218] Example 3.

[0219] (Electrolyte manufacturing)

[0220] An electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 in a non-aqueous organic solvent to have a concentration of LiPF6 of 1.2 M (ethylene carbonate content: 19.40 wt% / LiPF6 content: 14.43 wt%) (see Table 1 below).

[0221]

[0222] (Secondary battery manufacturing)

[0223] An electrolyte and a 4680 cell containing the same were manufactured in the same manner as in Example 1, except that the electrolyte (38 g) manufactured above was injected.

[0224]

[0225] Example 4.

[0226] (Secondary battery manufacturing)

[0227] An electrolyte and a 4680 cell (form factor ratio: 0.58) containing the electrolyte were manufactured in the same manner as in Example 3, except that the electrolyte (31 g) of Example 3 was injected.

[0228]

[0229] Example 5.

[0230] (Electrolyte manufacturing)

[0231] An electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 in a non-aqueous organic solvent to have a concentration of LiPF6 of 1.05 M (ethylene carbonate content: 19.76 wt% / LiPF6 content: 14.40 wt%) (see Table 1 below).

[0232]

[0233] (Secondary battery manufacturing)

[0234] An electrolyte and a 4680 cell containing the same were manufactured in the same manner as in Example 1, except that the prepared electrolyte (31 g) was injected.

[0235]

[0236] Example 6.

[0237] (Electrolyte manufacturing)

[0238] An electrolyte was prepared by adding LiPF6 to a non-aqueous organic solvent containing ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 to a concentration of 1.2 M, and then adding 3 wt% of vinylene carbonate (VC) and 0.5 wt% of 1,3-propanesultone (1,3-PS) (ethylene carbonate content: 19.40 wt% / LiPF6 content: 14.43 wt%) (see Table 1 below).

[0239]

[0240] (Secondary battery manufacturing)

[0241] An electrolyte and a 4680 cell containing the same were manufactured in the same manner as in Example 1, except that the electrolyte (38 g) manufactured above was injected.

[0242]

[0243] Example 7.

[0244] (Electrolyte manufacturing)

[0245] An electrolyte was prepared by adding LiPF6 to a non-aqueous organic solvent containing ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 to a concentration of 1.2 M, and then adding 3 wt% of vinylene carbonate (VC), 0.5 wt% of 1,3-propanesultone (1,3-PS), and 1 wt% of fluoroethylene carbonate (FEC) (ethylene carbonate content: 19.17 wt% / LiPF6 content: 14.40 wt%) (see Table 1 below).

[0246]

[0247] (Secondary battery manufacturing)

[0248] An electrolyte and a 4680 cell containing the same were manufactured in the same manner as in Example 1, except that the electrolyte (38 g) manufactured above was injected.

[0249]

[0250] Example 8.

[0251] (Electrolyte manufacturing)

[0252] An electrolyte was prepared by adding LiPF6 to a non-aqueous organic solvent containing ethylene carbonate (EC), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 to a concentration of 1.2 M, and then adding 3 wt% of vinylene carbonate (VC) and 0.5 wt% of ethylene sulfate (ESa) (ethylene carbonate content: 19.40 wt% / LiPF6 content: 14.43 wt%) (see Table 1 below).

[0253]

[0254] (Secondary battery manufacturing)

[0255] An electrolyte and a 4680 cell containing the same were manufactured in the same manner as in Example 1, except that the electrolyte (38 g) manufactured above was injected.

[0256]

[0257] Comparative Example 1.

[0258] (Secondary battery manufacturing)

[0259] An electrolyte and a 4680 cell (form factor ratio: 0.58) containing the same were manufactured in the same manner as in Example 3, except that the electrolyte (43 g) of Example 3 was injected.

[0260]

[0261] Comparative Example 2.

[0262] (Secondary battery manufacturing)

[0263] An electrolyte and a 4680 cell (form factor ratio: 0.58) containing the electrolyte were manufactured in the same manner as in Example 3, except that the electrolyte (25 g) of Example 3 was injected.

[0264]

[0265] Comparative Example 3.

[0266] (Electrolyte manufacturing)

[0267] An electrolyte was prepared by adding LiPF6 to a mixed non-aqueous organic solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 to obtain a concentration of 0.95 M (ethylene carbonate content: 20.00 wt% / LiPF6 content: 11.89 wt%) (see Table 1 below).

[0268]

[0269] (Secondary battery manufacturing)

[0270] An electrolyte and a 4680 cell containing the same were manufactured in the same manner as in Example 1, except that the electrolyte (31 g) manufactured above was injected.

[0271]

[0272] Comparative Example 4.

[0273] (Electrolyte manufacturing)

[0274] An electrolyte was prepared by adding LiPF6 to a non-aqueous organic solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 to obtain a concentration of 1.6 M (ethylene carbonate content: 18.50 wt% / LiPF6 content: 17.73 wt%) (see Table 1 below).

[0275]

[0276] (Secondary battery manufacturing)

[0277] An electrolyte and a 4680 cell containing the same were manufactured in the same manner as in Example 1, except that the electrolyte (38 g) manufactured above was injected.

[0278]

[0279] Comparative Example 5.

[0280] (Electrolyte manufacturing)

[0281] An electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 in a non-aqueous organic solvent to have a LiPF6 concentration of 1.3 M (ethylene carbonate content: 19.17 wt% / LiPF6 content: 15.41 wt%) (see Table 1 below).

[0282]

[0283] (Secondary battery manufacturing)

[0284] Average particle diameter D 50 This positive electrode active material (Li(Ni)) has a unimodal particle size distribution of 3 ㎛ and is in the form of a single particle. 0.90 Mn 0.03Co 0.05 Al 0.02 )O2) and Carbon nanotubes and PVDF binder were added and mixed in a weight ratio of 97.8:0.6:1.6 in N-methylpyrrolidone to prepare a cathode slurry. The cathode slurry was applied to one side of an aluminum current collector sheet, dried at 120°C, and then rolled to prepare a cathode plate.

[0285] A negative electrode slurry was prepared by adding and mixing a negative electrode active material (graphite and SiO = 95:5 weight ratio), a conductive agent (super C), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) in a weight ratio of 96:2:1.5:0.5 to water. The negative electrode slurry was applied to one surface of a copper current collector sheet, dried at 150°C, and then rolled to prepare a negative electrode plate.

[0286] An electrode assembly (diameter of core part: 7 mm) was manufactured by interposing a separator between the positive and negative plates manufactured as described above, stacking the separator / positive plate / separator / negative plate in that order, and then winding the assembly. The electrode assembly manufactured as described above was inserted into a cylindrical battery can (diameter: 46 mm, height: 70 mm), and the electrolyte (38 g) was injected to manufacture a 4670 cell (form factor ratio: 0.657).

[0287]

[0288] Comparative Example 6.

[0289] (Secondary battery manufacturing)

[0290] A 46120 cell (form factor ratio: 0.383) was manufactured in the same manner as in Comparative Example 5, except that the manufactured electrode assembly (core diameter: 7 mm) was inserted into a cylindrical battery can (diameter: 46 mm, height: 120 mm) and then electrolyte (38 g) was injected.

[0291]

[0292] EC content in electrolyte (wt%)LiPF6 content in electrolyte (wt%)Whether additives are includedElectrolyte volume (g)Form factorFormula (1)*Example 119.1715.41×380.5755.69Example 219.1715.41×310.5756.98Example 319.4014.43×380.5756.15Example 419.4014.43×310.5757.54Example 519.7614.40×310.5758.58Example 619.4014.43○380.5756.15Example 719.1714.40○380.5756.09Example 819.4014.43○380.5756.15Comparative example 119.4014.43×430.5755.44Comparative example 219.4014.43×250.5759.35Comparative example 320.0011.89×310.5759.44Comparative example 418.5017.73×380.5754.79Comparative example 519.1715.41×430.6574.98Comparative example 619.1715.41×380.3838.54

[0293] In the above Table 1, Equation (1)* It represents the value calculated from ×100.

[0294] Experimental example

[0295] Experimental Example 1. AC Resistance Evaluation

[0296] The secondary batteries manufactured in Examples 1, 3, 5, 6, and 8, respectively, and the secondary batteries manufactured in Comparative Examples 1 to 4 and 6, respectively, were formed by repeating two cycles (charge: 4.2 V CC, discharge: 2.5 V CC) at 25°C with a current of 25 A (0.1 C), and then CC / CV charging under the conditions of 4.2 V 8.33 A (0.3 C, 0.05 C cut-off) and CC discharging under the conditions of 2.5 V 8.33 A (0.3 C) were repeated three times. Afterwards, AC resistance was measured in the range of 1 kHz using a Multi-impedance analyzer (Biologic, Model: VMP3) at a temperature of 25°C and a SOC (State Of Charge) of 30%, and the results are shown in Table 2 below.

[0297]

[0298] Experimental Example 2. Evaluation of DC Resistance (Direct Current Internal Resistance)

[0299] The secondary batteries manufactured in Examples 1, 3, 5, 6 and 8, respectively, and the secondary batteries manufactured in Comparative Examples 1 to 4 and 6, respectively, were formed and cycled three times in the same manner as in Experimental Example 1, and then fully charged under the conditions of 4.2 V 8.33 A (0.3 C, 0.05 C cut-off), discharged to 50% of SOC at room temperature, and discharged for 10 seconds at a current of 0.5 C, and the voltage drop that occurred was recorded, and the DC resistance (DC-IR) value was measured using Ohm's law (R=V / I), and the results are shown in Table 2 below.

[0300]

[0301] ACIR (mOhm) DCIR (mOhm) Example 19795 Example 39593 Example 59787 Example 69593 Example 89692 Comparative Example 1100100 Comparative Example 2115130 Comparative Example 3118121 Comparative Example 4102105 Comparative Example 6120135

[0302]

[0303] Referring to Table 2 above, it can be seen that the secondary batteries manufactured in Examples 1, 3, 5, 6, and 8 have improved cell performance compared to the secondary batteries manufactured in Comparative Examples 1 to 4 and 6, with the increase in resistance being suppressed.

[0304] That is, when comparing the cells of Examples 3, 6, and 8 with Comparative Examples 1 and 2, it can be seen that even when the cell dimensions and electrolyte compositions are the same, the value calculated from Equation (1) considering the electrolyte injection amount is inferior to the cells of Comparative Examples 1 and 2 in that the resistance increases and the cell performance is inferior to the cells of Examples 3, 6, and 8 in that the cells deviate from the conditions of the present invention.

[0305] In addition, when comparing the secondary battery manufactured in Example 1 with the secondary battery manufactured in Comparative Example 4, it can be seen that even when the cell dimensions and electrolyte solution amount are the same, the value calculated from Equation (1) considering the lithium salt and ethylene carbonate content included in the electrolyte is inferior to the cell of Comparative Example 4, which deviates from the conditions of the present invention, in terms of resistance, compared to the cell of Example 1, resulting in inferior cell performance.

[0306] In addition, when comparing the secondary battery manufactured in Example 5 with the secondary battery manufactured in Comparative Example 3, it can be seen that even when the cell dimensions and electrolyte solution amount are the same, the value calculated from Equation (1) considering the lithium salt and ethylene carbonate contents included in the electrolyte is inferior to the cell of Comparative Example 3, which deviates from the conditions of the present invention, in terms of resistance, compared to the cell of Example 5, resulting in inferior cell performance.

[0307] Meanwhile, in the case of the secondary battery of Comparative Example 6, even if the electrolyte composition and the amount of electrolyte solution are the same as in Example 1, it can be confirmed that the resistance increases compared to the secondary batteries of the examples, as the form factor ratio is outside the range of the present invention, the wetting property is reduced due to the insufficient amount of electrolyte solution.

[0308]

[0309] Experimental Example 3.

[0310] Each cell manufactured in Examples 1 to 8 and Comparative Examples 1 to 6 was subjected to constant current-constant voltage charging up to 4.2 V at 1.0 C-rate at room temperature (25°C), then discharged with a 0.5 C cut off, and the initial capacity was measured.

[0311] Next, constant current-constant voltage charging was performed at a high temperature (40°C) to 4.2 V at a C-rate of 1.0 C, and then discharged to 2.5 V at a C-rate of 0.2 C, which constituted one cycle, and 100 cycles of charge-discharge were performed. The capacity retention rate after 100 cycles at 40°C was measured compared to the initial capacity after the first cycle, and the results are shown in Table 3 below.

[0312] Capacity retention rate (%) after 100 cycles Example 195 Example 298 Example 393 Example 497 Example 596 Example 693 Example 795 Example 894 Comparative Example 1 <80 Comparative Example 2 <80 Comparative Example 390 Comparative Example 485 Comparative Example 589 Comparative Example 687

[0313]

[0314] Referring to Table 3 above, it can be seen that the capacity retention rate after 100 cycles is significantly improved in the lithium secondary batteries of Examples 1 to 8 of the present invention compared to the lithium secondary batteries of Comparative Examples 1 to 6.

[0315]

[0316] Description of the symbol

[0317] 10: Anode 11: Cathode

[0318] 12: Separator 20: Current collector

[0319] 21, 21a: Active material layer 22, 22a, 22c: Non-conductive layer

[0320] 24: Insulating layer

[0321] 140, 170: Cylindrical battery

[0322] 141: Jelly-roll type electrode assembly

[0323] 142, 171: Battery case

[0324] 143, 178: Sealed body

[0325] 144: First collector plate 145, 176: Second collector plate

[0326] 146a: Non-conductive part of the positive electrode

[0327] 146b: Non-conductive part of the negative plate

[0328] 146: Insulator 152: Venting

[0329] 172: Rivet terminal

[0330] 173: Second gasket 178b: First gasket

[0331] 173a: Gasket exposed part 173b: Gasket inserted part

[0332] 147, 180: Beading section 148: Crimping section

[0333] 149: Lead 172a: Terminal exposed part

[0334] 173b: Terminal insert 174: Insulating cap

Claims

1. A lithium secondary battery comprising a battery case; an electrode assembly housed inside the battery case; and an electrolyte. The above electrode assembly includes a positive electrode including a positive active material, a separator, and a negative electrode including a negative active material, The above electrolyte contains LiPF6 as a lithium salt and ethylene carbonate as an organic solvent. The above lithium secondary battery is a lithium secondary battery having a ratio of the diameter (r) to the height (h) of the battery case (form factor ratio) of 0.4 or more and satisfying the condition of the following equation (1): [Formula (1)] 5.6 ≤ ×100≤8.6 (In the above equation (1), h is the height of the battery case (mm), r is the diameter of the battery case (mm), W LiPF6 is the content of LiPF6 in percentage (%) relative to the total weight of the electrolyte, W EC is the content of ethylene carbonate in percentage (%) relative to the total weight of the electrolyte. W EL refers to the weight (g) of the total electrolyte contained in a lithium secondary battery.

2. In paragraph 1, The above lithium secondary battery is a cylindrical lithium secondary battery having a ratio of the diameter (r) to the height (h) of the battery case (form factor ratio) of 0.4 to 0.

6.

3. In paragraph 1, The above lithium secondary battery is a lithium secondary battery having 46110 cells, 48110 cells, 4880 cells or 4680 cells.

4. In paragraph 1, The lithium secondary battery is a lithium secondary battery having a tab-less structure in which the non-conductive portion of the positive electrode and the negative electrode are not formed with an active material layer on at least a portion of the positive electrode and the negative electrode, and in which the non-conductive portion of the positive electrode or the non-conductive portion of the negative electrode is defined as an electrode tab.

5. In paragraph 4, A lithium secondary battery, wherein the non-coated portion of the positive electrode and the non-coated portion of the negative electrode are formed along the direction in which the electrode assembly is wound on one end of the positive electrode and the negative electrode, respectively, and a current collecting plate is bonded to each of the non-coated portion of the positive electrode and the non-coated portion of the negative electrode, and the current collecting plate is connected to an electrode terminal.

6. In paragraph 5, The above-mentioned anode and cathode portions are processed into a plurality of independently bendable segments, A lithium secondary battery, wherein at least some of the plurality of segments are bent toward the winding center of the electrode assembly.

7. In paragraph 6, A lithium secondary battery in which at least some of the plurality of folded segments overlap on the upper and lower sides of the electrode assembly, and the current collecting plate is bonded to the plurality of overlapped segments.

8. In paragraph 1, The above positive electrode active material is a lithium transition metal oxide containing Ni and Co, A lithium secondary battery wherein the lithium transition metal oxide satisfies the following formula (2): Equation (2): 18 ≤ X Ni / X Co ≤ 48 (In the above equation (2), X Ni is the molar percentage of Ni among the total metals excluding lithium in the above lithium transition metal oxide, and X Co is the molar percentage of Co among the total metals excluding lithium in the above lithium transition metal oxide.

9. In paragraph 8, A lithium secondary battery wherein the lithium transition metal oxide is represented by the following [chemical formula 1]. [Chemical Formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above chemical formula 1, M 1 is Mn, Al or a combination thereof, and M 2 is at least one selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and 0.8≤a≤1.2, 0.85 <b<1, 0<c<0.06, 0<d<0.15, 0≤e≤0.1임.

10. In paragraph 9, The above lithium transition metal oxide is Li(Ni 0.90 Mn 0.05 Co 0.05 )O 2, Li(Ni) 0.94 Co 0.04 Mn 0.02 )O 2, 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 ) Lithium secondary battery which is O2.

11. In paragraph 1, The above negative electrode active material is a mixture of a carbon-based negative electrode active material and a silicon-based negative electrode active material, A lithium secondary battery wherein the carbon-based negative electrode active material and the silicon-based negative electrode active material are included in a weight ratio of 95:5 to 99:

1.

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

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