Cylindrical lithium secondary battery

Abstract

The present invention relates to a cylindrical lithium secondary battery comprising: an electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator provided between the positive electrode plate and the negative electrode plate are wound in one direction; a battery can accommodating the electrode assembly; an electrolyte injected into the battery can; and a sealing body that seals the open end of the battery can, in which the positive electrode plate and the negative electrode plate each include a non-coated portion in which an active material layer is not formed, and each have a structure in which at least a portion of the non-coated portion of the positive electrode plate or the negative electrode plate defines a tab, a form factor ratio of the cylindrical lithium secondary battery is 0.4 or more, a core portion diameter of the electrode assembly is 5 mm to 8 mm, and a core portion diameter of the electrode assembly is 5 mm to 8 mm. The electrolyte comprises a lithium salt, an organic solvent and an additive, the additive comprises a compound of formula 1, a cyclic carbonate compound and 1, 3-propane sultone in a weight ratio of 1: 0.5: 0.2 to 1: 20: 10, and the content of the compound of formula 1 is 0.5 wt% to 5.0 wt% based on the total amount of the electrolyte.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to Korean Patent Application Nos. 10 - 2022 - 0182368, filed on December 22, 2022, and 10 - 2023 - 0187677, filed on December 20, 2023, the disclosures of which are incorporated herein by reference. Technical field

[0003] The present invention relates to a cylindrical lithium secondary battery. Background art

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

[0005] Lithium secondary batteries can be classified into cylindrical, prismatic, and pouch - type batteries. The cylindrical battery is formed as follows: by sequentially laminating sheet - shaped positive and negative electrode plates and a separator and then winding them in one direction to prepare an electrode assembly, and then accommodating the electrode assembly in a cylindrical battery can, and then covering the upper part of the battery can with a cover plate to form a sealed cylindrical battery. The positive and negative electrode plates are respectively provided with strip - shaped positive and negative electrode tabs, and the positive and negative electrode tabs are respectively connected to electrode terminals to be electrically connected to an external power source. For reference, the positive terminal is the cover plate, and the negative terminal is the battery can. However, for a conventional cylindrical battery having such a structure, due to the current concentration on the strip - shaped tabs, there are problems of high resistance, generation of a large amount of heat, and poor current collection efficiency.

[0006] Due to the increasing demand for high - capacity batteries with the technological advancements of recent electric vehicles, it is necessary to develop large - sized cylindrical batteries with a larger volume. For the small - sized cylindrical batteries commonly used in the past, that is, cylindrical batteries with a form factor of 1865 or 2170, since the capacity is small, the resistance or heat generation does not seriously affect the battery performance.

[0007] However, in the case of applying the specifications of a conventional small cylindrical battery as they are to a large cylindrical battery, serious battery safety problems will occur. That is, as the size of the battery increases, the amount of heat generated and the amount of gas generated in the battery also increase. Among them, since the temperature and pressure in the battery increase due to heat and gas, the battery may catch fire or explode. To prevent this, the heat and gas in the battery must be appropriately discharged to the outside. For this purpose, the cross-sectional area of the battery that serves as a channel for discharging heat to the outside of the battery must be increased to match the increase in volume. However, since the increase in the normal cross-sectional area does not reach the increase in volume, as the size of the battery increases, the amount of heat generated in the battery increases. As a result, the risk of explosion increases, and problems such as a decrease in output occur. In addition, in the case of rapid charging at high voltage, the following problems may also occur: A large amount of heat is generated around the tab in a short time, and the battery catches fire.

[0008] Therefore, it is necessary to develop a cylindrical battery that can maintain high safety even at high output. Summary of the Invention

[0009] [Technical Problem]

[0010] One aspect of the present invention provides a cylindrical lithium secondary battery that controls the amount of gas generated in the battery by using an electrolyte having a specific composition, thereby improving electrolyte impregnation properties, so that the cylindrical lithium secondary battery can maintain high safety even at high output.

[0011] [Technical Solution]

[0012] According to one embodiment, the present invention provides a cylindrical lithium secondary battery, comprising: an electrode assembly obtained by winding a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate in one direction; a battery can accommodating the electrode assembly; an electrolyte injected into the battery can; and a sealing body sealing an open end of the battery can, wherein each of the positive electrode plate and the negative electrode plate includes a non-coated portion where no active material layer is formed, and each has a structure in which at least a part of the non-coated portion of the positive electrode plate or the negative electrode plate defines an electrode tab, the form factor ratio of the cylindrical lithium secondary battery is 0.4 or more, the diameter of the core portion of the electrode assembly is 5 mm to 8 mm, and the electrolyte includes a lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive includes a compound represented by Formula 1, a cyclic carbonate compound, and 1,3-propane sultone, and based on the total amount of the electrolyte, the content of the compound represented by Formula 1 is 0.5 wt% to 5.0 wt%, and the weight ratio of the compound represented by Formula 1, the cyclic carbonate compound, and 1,3-propane sultone is 1:0.5:0.2 to 1:20:10.

[0013] [Formula 1]

[0014]

[0015] In Formula 1, n is an integer from 3 to 10.

[0016] According to another embodiment, the present invention provides a battery pack including the cylindrical lithium secondary battery of the present invention.

[0017] [Advantageous Effects]

[0018] The cylindrical lithium secondary battery of the present invention having a shape factor ratio within a specific range can control the gas generation amount in the battery by using an electrolyte containing a specific additive in a specific content ratio, thereby adjusting the internal pressure of the battery cell. Therefore, by maximizing the electrolyte impregnation property of the electrode assembly, high thermal safety can be ensured even at high output. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following drawings attached to this specification illustrate the preferred embodiments of the present invention through examples, and together with the detailed description of the present invention given below, can further help to understand the technical concept of the present invention. Therefore, the present invention should not be construed as only having the matters shown in these drawings.

[0020] Figure 1 is a view illustrating the stacked state of the electrode assembly before winding of the present invention.

[0021] Figure 2 is a cross-sectional view illustrating the structure of the electrode plate of the electrode assembly of the embodiment of the present invention.

[0022] Figure 3 is a cross-sectional view illustrating the structure of the cylindrical battery with an earless structure of the embodiment of the present invention.

[0023] Figure 4 is a cross-sectional view illustrating the structure of the cylindrical battery with an earless structure of another embodiment of the present invention.

[0024] Figure 5 is a view for explaining the structure of the electrode assembly of the example of the present invention.

[0025] Figure 6 is a view for explaining the battery pack of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Hereinafter, the present invention will be described in more detail.

[0027] It will be understood that the words or terms used in the specification and claims should not be construed as having the meanings defined in a commonly used dictionary, and it will be further understood that, based on the principle that the inventor can appropriately define the meanings of the words or terms to best explain the present invention, the words or terms should be construed as having meanings consistent with their meanings in the context of the relevant field and the technical concept of the present invention.

[0028] In the present invention, the expression "primary particle" refers to a particle unit that does not have grain boundaries in appearance when observed at a magnification of 5,000 to 20,000 times with a scanning electron microscope. The expression "average particle size of primary particles" refers to the arithmetic average of the particle sizes calculated after measuring the particle sizes of the primary particles observed in a scanning electron microscope image.

[0029] In the present invention, the expression "secondary particle" is a particle formed by the aggregation of a plurality of primary particles. In the present invention, a secondary particle formed by the aggregation of 10 or fewer primary particles is called a quasi-single particle in order to distinguish it from a conventional secondary particle formed by the aggregation of dozens to hundreds of primary particles.

[0030] In the present invention, "average particle size D 50 " represents the particle size at 50% based on the volume cumulative particle size distribution of the positive electrode active material powder, where the average particle size D 50 can be measured by the laser diffraction method. For example, the average particle size can be measured as follows: The positive electrode active material powder is dispersed in a dispersion medium, and then the dispersion medium is introduced into a commercially available laser diffraction particle size measuring instrument (such as Microtrac MT 3000), and then irradiated with ultrasonic waves at an output of 60 W and a frequency of 28 kHz to obtain a volume cumulative particle size distribution diagram, and then the particle size corresponding to 50% of the volume cumulative amount is obtained.

[0031] "Consisting essentially of A" in the present invention means containing component A as the main component, where, for example, this means that the content of component A is 95% by weight to 100% by weight, preferably 98% by weight to 100% by weight, more preferably 99% by weight to 100% by weight.

[0032] Depending on the gas generation degree in the battery cell and the internal pressure of the battery cell, conventional large cylindrical lithium secondary batteries can have different electrolyte impregnation properties. In particular, in the case of using an electrode assembly with a core diameter of 5 mm to 8 mm in a large cylindrical battery, it is difficult to control the electrolyte impregnation property, so safety cannot be fully ensured. On the contrary, since the cylindrical lithium secondary battery of the present invention can control the internal pressure of the battery cell by adjusting the gas generation amount in the battery cell by using an electrolyte with a specific composition, the electrolyte impregnation property of the electrode assembly can be improved, and thus the effect of improving the thermal stability of the battery can be obtained.

[0033] Hereinafter, the structure of the cylindrical lithium secondary battery of the present invention will be described in detail.

[0034] Electrode assembly

[0035] The electrode assembly has a structure in which a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate are wound in one direction.

[0036] In Figure 1 the stacked structure of the electrode assembly of the present invention before winding is shown, and in Figure 2 the cross-sectional structure of the electrode plate (positive electrode plate or negative electrode plate) of the present invention is shown.

[0037] Referring to Figure 1 and Figure 2 , the electrode assembly A of the present invention can be prepared by winding a stacked body formed by sequentially stacking at least once a separator 12, a positive electrode plate 10, a separator 12, and a negative electrode plate 11 in one direction X.

[0038] In this case, each of the positive electrode plate 10 and the negative electrode plate 11 has a structure in which an active material layer 21 is formed on a long-strip-shaped current collector 20, and may include an uncoated portion 22 where the active material layer 21 is not formed in a partial region of the current collector 20.

[0039] If the positive electrode plate 10 and the negative electrode plate 11 including the uncoated portion 22 as described above are used, a battery having a structure without an electrode tab can be realized, in which no separate electrode tab is included, and at least a part of the uncoated portions of the positive electrode plate 10 and the negative electrode plate 11 define the electrode tab.

[0040] Specifically, the uncoated portion 22 may be formed in a long strip shape at one end of the current collector 20 in the winding direction X, and a battery having a structure without an electrode tab can be realized by bonding a current collecting plate to each of the uncoated portions of the positive electrode plate and the negative electrode plate and connecting the current collecting plate to an electrode terminal.

[0041] For example, a battery having a structure without an electrode tab can be prepared by the following method. First, a separator, a positive electrode plate, a separator, and a negative electrode plate are sequentially stacked such that the uncoated portions 22 of the positive electrode plate 10 and the negative electrode plate 11 are disposed in opposite directions, and then wound in one direction to prepare an electrode assembly. Then, the uncoated portions 22 of the positive electrode plate and the negative electrode plate are bent toward the winding center C, and then the current collecting plates are respectively welded and joined to the uncoated portions of the positive electrode plate and the negative electrode plate, and the current collecting plates are connected to the electrode terminals, whereby a battery having a structure without an electrode tab can be prepared. Since the current collecting plate has a larger cross-sectional area than the strip-shaped electrode tab, and the resistance is inversely proportional to the cross-sectional area of the path through which the current flows, when the secondary battery is formed with the above structure, the internal resistance of the battery cell can be significantly reduced.

[0042] The non-coated portions of the positive electrode plate and the negative electrode plate can be processed into a form of a plurality of independently bendable sections, and at least a part of the plurality of sections can be bent toward the winding center C of the electrode assembly.

[0043] The current collectors of the positive electrode plate and the negative electrode plate can be processed by a metal foil cutting process (such as laser scribing, ultrasonic cutting, and punching) to form the sections.

[0044] In the case where the non-coated portions of the positive electrode plate and the negative electrode plate are processed into a form of a plurality of sections, by reducing the stress applied to the non-coated portions during the bending process, deformation or damage of the non-coated portions can be prevented, and the welding characteristics with the current collector plate can be improved.

[0045] The current collector plate and the non-coated portion are usually joined by welding. In this case, in order to improve the welding characteristics, a strong pressure must be applied to the welding area of the non-coated portion to bend the non-coated portion as flat as possible. However, the shape of the non-coated portion may be irregularly distorted and deformed during this bending process, and the deformed portion may contact the electrode with the opposite polarity, resulting in an internal short circuit or microcracks appearing in the non-coated portion. However, if the non-coated portions of the positive electrode plate and the negative electrode plate are processed into a form of a plurality of independently bendable sections, the stress applied to the non-coated portions during the bending process is reduced, so that deformation and damage of the non-coated portions can be minimized.

[0046] In addition, in the case where the non-coated portion is processed into the form of the sections as described above, overlap occurs between the plurality of sections during the bending process. As a result, the welding strength with the current collector plate increases, and the problem that the laser beam penetrates into the electrode assembly to ablate the separator or the active material when using the latest technology (such as laser welding) can be prevented. Preferably, at least a part of the plurality of bent sections can overlap at the upper and lower ends of the electrode assembly, and the current collector plate can be joined to the overlapping plurality of sections.

[0047] As Figure 5 shown, the electrode assembly of the present invention can be formed into a structure in which an insulating layer 24 is additionally formed on the positive electrode plate 10. Specifically, the insulating layer 24 can be formed to cover a part of the positive electrode active material layer and a part of the non-coated portion along a direction parallel to the winding direction of the electrode assembly.

[0048] For a battery with a tabless structure that uses the non-coated portion 22c of the positive electrode plate 10 and the non-coated portion 22a of the negative electrode plate 11 as electrode tabs, an electrode assembly is formed such that the positive electrode plate 10 protrudes above the separator 12, the negative electrode plate 11 protrudes below the separator 12, and the protruding positive electrode plate 10 and / or negative electrode plate 11 are bent and then joined to the current collector plate. When the positive electrode plate 10 or the negative electrode plate 11 is bent as described above, the current collector of the positive electrode plate 10 or the negative electrode plate 11 crosses the separator and is disposed near the electrode of the opposite polarity. As a result, there is a possibility that the positive electrode plate and the negative electrode plate are in electrical contact to cause an internal short circuit. However, as Figure 5 shown, when an insulating layer 24 is formed to cover a part of the positive active material layer and the non-coated portion, since the insulating layer 24 can prevent electrical contact between the positive electrode plate 10 and the negative electrode plate 11, a short circuit in the battery can be prevented.

[0049] Preferably, the insulating layer 24 can be disposed on at least one surface of the current collector of the positive electrode plate 10, and preferably, it can be disposed on both surfaces of the positive electrode plate 10.

[0050] In addition, the insulating layer 24 can be formed in the region of the positive electrode plate 10 where the active material layer 21a facing the negative electrode plate 11 can be located. For example, on the surface of the non-coated portion 22c of the positive electrode plate 10 facing the negative electrode plate 11 after bending, the insulating layer 24 can be formed by extending to one end of the non-coated portion 22c. However, for the surface opposite to the surface facing the negative electrode plate 11 after bending, advantageously, the insulating layer 24 is only formed on a part of the non-coated portion 22c, for example, before the bending point of the non-coated portion 22c. The reason is that if the insulating layer 24 is formed in the entire region of the surface of the non-coated portion opposite to the surface facing the negative electrode plate 11, the function of the tab may not be achieved because electrical contact with the current collector plate cannot be made.

[0051] The insulating layer 24 can be used as long as it can ensure insulation performance while being attached to the positive electrode plate, and its material or composition is not particularly limited. For example, the insulating layer can be an insulating coating layer or an insulating tape, and the insulating coating layer can contain an organic binder and inorganic particles. In this case, the organic binder can be styrene-butadiene rubber (SBR), and the inorganic particles can be alumina, but it is not limited thereto.

[0052] The diameter of the core part of the electrode assembly of the present invention can be 5 mm or more, specifically 5 mm to 8 mm. When the diameter of the core part of the electrode assembly satisfies the above range, the defect rate can be suppressed during the winding process for preparing the electrode assembly, and sufficient space for injecting electrolyte can be ensured in the cylindrical secondary battery. When the diameter of the core part of the electrode assembly is less than 5 mm, problems such as gas exhaust may occur due to the increase in the internal pressure of the battery cell caused by the gas generated by the electrolyte during charging and discharging. On the contrary, when the diameter of the core part of the electrode assembly is greater than 8 mm, the energy density per unit volume of the battery cell decreases and the wettability to the electrolyte decreases, so the performance of the battery cell may deteriorate. In particular, for a large cylindrical battery with a form factor of 0.4 or more, maintaining an appropriate level of internal pressure can maximize the performance of the battery cell by improving the wettability of the electrolyte to the electrode assembly. Therefore, in the present invention, by using a combination of an electrolyte with a specific additive composition and an electrode assembly with a core diameter of 5 mm or more (specifically 5 mm to 8 mm), the gas generation amount in the battery cell is adjusted, and accordingly, the internal pressure of the battery cell is maintained at an appropriate level, so the electrolyte impregnation property of the electrode assembly can be improved.

[0053] The total diameter of the electrode assembly can be the conventional diameter corresponding to a large cylindrical battery with a form factor of 0.4 or more.

[0054] Next, each component of the electrode assembly of the present invention will be described in more detail.

[0055] (1) Positive electrode plate

[0056] The positive electrode plate can be formed in a structure in which a positive electrode active material layer is formed on one or both sides of a long sheet-shaped positive electrode current collector, and the positive electrode active material layer can include a positive electrode active material, a conductive agent, and a binder.

[0057] Specifically, the positive electrode plate can be prepared by the following method: dispersing a positive electrode active material, a conductive agent, and a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and water to prepare a positive electrode slurry, applying the positive electrode slurry on one or both sides of a long sheet-shaped positive electrode current collector, removing the solvent of the positive electrode slurry through a drying process, and performing rolling. A positive electrode plate including an uncoated portion can be prepared by the following method: when applying the positive electrode slurry, the positive electrode slurry is not applied to a partial area of the positive electrode current collector, for example, one end of the positive electrode current collector.

[0058] As the positive electrode current collector, various positive electrode current collectors used in the art can be used. For example, as the positive electrode current collector, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc. can be used. The thickness of the positive electrode current collector can generally be 3 μm to 500 μm, and micro unevenness can be formed on the surface of the current collector to improve the adhesion of the positive electrode active material. For example, the positive electrode current collector can be used in various shapes, such as a film, sheet, foil, net, porous body, foam body, non-woven fabric body, etc.

[0059] In addition, the positive electrode plate of the present invention can use a positive electrode active material having a nickel (Ni) content of 80 mol% or more in transition metals other than lithium in order to achieve high capacity. Specifically, a positive electrode active material having a Ni content of 80 mol% or more to less than 100 mol%, 82 mol% or more to less than 100 mol%, or 83 mol% or more to less than 100 mol% in transition metals other than lithium can be used as the positive electrode active material, and preferably, the positive electrode active material can contain a lithium nickel-based oxide represented by the following [Formula 2].

[0060] [Formula 2]

[0061] Li a Ni b Co c M 1 d M 2 e O2

[0062] In Formula 2, M 1 can be manganese (Mn), aluminum (Al), or a combination thereof, and can preferably be Mn or Mn and Al.

[0063] M 2 can be at least one selected from the group consisting of zirconium (Zr), tungsten (W), yttrium (Y), barium (Ba), calcium (Ca), titanium (Ti), magnesium (Mg), tantalum (Ta), and niobium (Nb), can preferably be at least one selected from the group consisting of Zr, Y, Mg, and Ti, and can be more preferably Zr, Y, or a combination thereof. The element M 2 is not necessarily included, but when an appropriate amount of the element M 2 is included, it can play a role in promoting grain growth or improving the crystal structure stability during the sintering process.

[0064] a represents the molar ratio of lithium in the lithium nickel-based oxide, wherein a can satisfy 0.8 ≤ a ≤ 1.2, or can satisfy 0.85 ≤ a ≤ 1.15, and specifically can satisfy 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.

[0065] b represents the molar ratio of nickel in the total metals other than lithium in the lithium nickel-based oxide. Among them, b can satisfy 0.85 ≤ b < 1, or can satisfy 0.86 ≤ b < 1, and specifically can satisfy 0.88 ≤ b < 1. When the molar ratio of nickel satisfies the above range, high energy density can be exhibited to achieve high capacity.

[0066] c represents the molar ratio of cobalt in the total metals other than lithium in the lithium nickel-based oxide. Among them, c can satisfy 0 < c < 0.15, or can satisfy 0 < c < 0.14, and specifically can satisfy 0.01 ≤ c ≤ 0.12. When the molar ratio of cobalt satisfies the above range, good resistance characteristics and output characteristics can be achieved.

[0067] d represents the molar ratio of element M in the total metals other than lithium in the lithium nickel-based oxide 1 and d can satisfy 0 < d < 0.15, or can satisfy 0 < d < 0.14, and specifically can satisfy 0.01 ≤ d ≤ 0.12. When the molar ratio of element M 1 satisfies the above range, the structural stability of the positive electrode active material is excellent.

[0068] e represents the molar ratio of element M in the total metals other than lithium in the lithium nickel-based oxide 2 and e can satisfy 0 ≤ e ≤ 0.1 or can satisfy 0 ≤ e ≤ 0.05.

[0069] When necessary, the positive electrode active material of the present invention may further include a coating layer on the surface of the lithium nickel-based oxide particles, and the coating layer includes at least one coating element selected from the group consisting of Al, Ti, W, boron (B), fluorine (F), phosphorus (P), Mg, Ni, cobalt (Co), iron (Fe), chromium (Cr), vanadium (V), copper (Cu), Ca, zinc (Zn), Zr, Nb, molybdenum (Mo), strontium (Sr), antimony (Sb), bismuth (Bi), silicon (Si), and sulfur (S). Preferably, the coating element may be Al, B, Co, or a combination thereof, and most preferably, the coating element may be B.

[0070] When the coating layer exists on the surface of the lithium nickel-based oxide particles, the coating layer inhibits the contact between the electrolyte and the lithium composite transition metal oxide. As a result, the effect of reducing the transition metal dissolution or gas generation caused by the side reaction with the electrolyte can be obtained.

[0071] Based on the total weight of the positive electrode active material layer, the content of the positive electrode active material can be 80% by weight to 99% by weight, preferably 85% by weight to 99% by weight, and more preferably 90% by weight to 99% by weight.

[0072] The form of the positive electrode active material is not particularly limited, and the positive electrode active material may be in the form of secondary particles formed by aggregation of a plurality of primary particles, a single particle form composed of one primary particle, or a combination thereof.

[0073] For secondary particles, since it is advantageous to form voids in the electrode, the electrolyte wetting effect can be improved. In the case of using a mixture of secondary particles and single particles, the secondary particles and single particles can be mixed and used in a ratio of 80:20, specifically 50:50.

[0074] Preferably, the positive electrode active material may include a single particle composed of one primary particle and / or a quasi-single particle which is an aggregate of 10 or fewer primary particles, or a combination thereof. A large cylindrical battery having high capacity and excellent safety can be obtained by using a positive electrode active material composed of a single particle composed of one primary particle and / or a quasi-single particle which is an aggregate of 10 or fewer primary particles, or a combination thereof.

[0075] Conventionally, spherical secondary particles formed by aggregating dozens to hundreds of primary particles are generally used as the positive electrode active material of a lithium secondary battery. However, for the positive electrode active material in the form of secondary particles formed by aggregating many primary particles as described above, there are the following problems: particle breakage is likely to occur (during the preparation of the positive electrode, the primary particles fall off during the rolling process), and the particles crack during the charge and discharge process. In the case of particle breakage or cracking in the positive electrode active material, due to the increased contact area with the electrolyte solution, there is a problem of increased gas generation caused by side reactions with the electrolyte solution. If the gas generation in the cylindrical battery increases, due to the increased pressure in the battery, there is a risk of battery explosion. In particular, in the case of an increase in the volume of the cylindrical battery, since the amount of the active material in the battery increases with the increase in volume, as a result, the gas generation amount also increases significantly, further increasing the risk of battery fire and / or explosion.

[0076] On the contrary, since the positive electrode active material in the form of a single particle composed of one primary particle or a quasi-single particle formed by aggregating 10 or fewer primary particles has higher particle strength compared to the conventional positive electrode active material in the form of secondary particles formed by aggregating dozens to hundreds of primary particles, particle breakage hardly occurs during the rolling process. In addition, for the positive electrode active material in the form of a single particle or a quasi-single particle, since the number of primary particles constituting the particle is small, the change caused by the volume expansion and contraction of the primary particles during the charge and discharge process is small, so the occurrence of cracking in the particles is significantly reduced.

[0077] Therefore, in the case of using a positive electrode active material composed of single particles and / or quasi-single particles, the amount of gas generation caused by particle breakage and internal cracking can be significantly reduced. Therefore, excellent safety can be achieved even in large cylindrical batteries.

[0078] Advantageously, based on the weight of the total positive electrode active material contained in the positive electrode active material layer, the content of the positive electrode active material composed of single particles and / or quasi-single particles is 95% by weight to 100% by weight, preferably 98% by weight to 100% by weight, more preferably 99% by weight to 100% by weight, and even more preferably 100% by weight. When the amount of single particles and / or quasi-single particles satisfies the above range, sufficient safety can be obtained when using this positive electrode active material in a large cylindrical battery.

[0079] The average particle diameter D of the positive electrode active material in the form of single particles and / or quasi-single particles of the present invention 50 can be 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less, for example, 0.5 μm to 5 μm, preferably 1 μm to 5 μm, more preferably 2 μm to 5 μm. When the average particle diameter D of the positive electrode active material 50 satisfies the above range, the increase in resistance can be minimized.

[0080] Since the interface between primary particles (as the diffusion path of lithium ions in the particles) of the positive electrode active material in the form of single particles and / or quasi-single particles is small, the lithium mobility is lower than that of the positive electrode active material in the form of secondary particles. As a result, the resistance may increase. As the particle size increases, this increase in resistance becomes more pronounced, and when the resistance increases, the capacity and output characteristics are adversely affected. Therefore, in the present invention, since single particles and / or quasi-single particles with an average particle diameter D 50 of 5 μm or less are used to minimize the diffusion distance of lithium ions in the particles, the increase in resistance can be suppressed.

[0081] The average particle diameter D of the primary particles of the positive electrode active material in the form of single particles and / or quasi-single particles 50 can be 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less, for example, 0.5 μm to 5 μm, preferably 1 μm to 5 μm, more preferably 2 μm to 5 μm. When the average particle diameter of the primary particles satisfies the above range, a positive electrode active material in the form of single particles and / or quasi-single particles with excellent electrochemical performance can be formed. If the average particle diameter of the primary particles is too small, the number of agglomerations of the primary particles constituting the positive electrode active material increases, reducing the effect of suppressing particle breakage during the rolling process. If the average particle diameter of the primary particles is too large, the diffusion path of lithium in the primary particles may increase, increasing the resistance and deteriorating the output characteristics.

[0082] In the present invention, advantageously, the positive electrode active material in the form of single particles and / or quasi-single particles has a unimodal particle size distribution. Conventionally, in order to improve the electrode density of the positive electrode active material layer, a bimodal positive electrode active material in which a large particle size positive electrode active material having a relatively large average particle size and a small particle size positive electrode active material having a relatively small average particle size are mixed has been widely used. However, for the positive electrode active material in the form of single particles and / or quasi-single particles, if the particle size increases, the resistance significantly increases due to the increase in the lithium migration path, and when large diameter particles are mixed and used, problems such as deterioration of capacity and output characteristics may occur. Therefore, in the present invention, by using a positive electrode active material having a unimodal distribution, an increase in resistance can be minimized.

[0083] Next, a conductive agent is used to provide conductivity to the electrode. Any conductive agent can be used without particular limitation as long as it has electronic conductivity and does not cause chemical changes in the battery. Specific examples of the conductive agent may be graphite powder, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, pyrolytic carbon black, carbon fiber, and carbon nanotube; metal powder or fiber, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and any one of them or a mixture of two or more of them can be used. Based on the total weight of the positive electrode active material layer, the content of the conductive agent can generally be 1% by weight to 30% by weight, preferably 1% by weight to 20% by weight, and more preferably 1% by weight to 10% by weight.

[0084] The binder improves the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples of the binder may be: fluororesin-based binders, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber-based binders, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose-based binders, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyol-based binders, including polyvinyl alcohol; polyolefin-based binders, including polyethylene or polypropylene; polyimide-based binders; polyester-based binders; and silane-based binders, and any one of them or a mixture of two or more of them can be used. Based on the total weight of the positive electrode active material layer, the content of the binder can be 1% by weight to 30% by weight, preferably 1% by weight to 20% by weight, and more preferably 1% by weight to 10% by weight.

[0085] If necessary, an insulating layer covering a part of the positive electrode active material layer and a part of the non-coated portion can be further formed on the positive electrode plate of the present invention. The insulating layer can be formed in a direction parallel to the winding direction of the electrode assembly.

[0086] (2) Negative electrode plate

[0087] The negative electrode plate can be formed into a structure in which a negative electrode active material layer is formed on one or both surfaces of a long sheet-shaped negative electrode current collector, and the negative electrode active material layer contains a negative electrode active material, a conductive agent, and a binder.

[0088] Specifically, the negative electrode plate can be prepared by the following method: dispersing a negative electrode active material, a conductive agent, and a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and water to prepare a negative electrode slurry, applying the negative electrode slurry to one or both surfaces of a long sheet-shaped negative electrode current collector, removing the solvent of the negative electrode slurry through a drying process, and performing roll pressing. The negative electrode plate including an uncoated portion can be prepared by the following method: when applying the negative electrode slurry, the negative electrode slurry is not applied to a partial region of the negative electrode current collector, for example, one end of the negative electrode current collector.

[0089] The negative electrode active material can include a negative electrode active material capable of reversibly inserting and extracting lithium.

[0090] Preferably, the negative electrode active material can include a silicon-based negative electrode active material. The silicon-based negative electrode active material can be Si, Si-Me alloy (where Me is at least one selected from the group consisting of Al, tin (Sn), Mg, Cu, Fe, lead (Pb), Zn, Mn, Cr, Ti, and Ni), SiO y (where 0 < y < 2), Si-C composite, or a combination thereof, and can preferably be SiO y (where 0 < y < 2). Since the silicon-based negative electrode active material has a high theoretical capacity, the capacity characteristics can be improved when the silicon-based negative electrode active material is included.

[0091] The silicon-based negative electrode active material can be doped with M b metal. In this case, M b metal can be a Group 1 metal element or a Group 2 metal element. Specifically, it can be lithium (Li), Mg, etc. Specifically, the silicon-based negative electrode active material can be Si, SiO b doped with M y (where 0 < y < 2) or Si-C composite. For the metal-doped silicon-based negative electrode active material, the capacity of the active material is reduced to a certain extent due to the doping element, but due to its high efficiency, a high energy density can be achieved.

[0092] In addition, the silicon-based negative electrode active material can also include a carbon coating layer on the particle surface. In this case, based on the total weight of the silicon-based negative electrode active material, the carbon coating amount can be 20% by weight or less, preferably 1% to 20% by weight.

[0093] In addition, when necessary, the negative electrode active material may further include a carbon-based negative electrode active material. The carbon-based negative electrode active material may be, for example, artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, soft carbon or hard carbon, but is not limited thereto.

[0094] When a mixture of a silicon-based negative electrode active material and a carbon-based negative electrode active material is used as the negative electrode active material, the mixing ratio (weight ratio) of the silicon-based negative electrode active material to the carbon-based negative electrode active material may be from 1:99 to 20:80, preferably from 1:99 to 15:85, more preferably from 1:99 to 10:90.

[0095] Based on the total weight of the negative electrode active material layer, the content of the negative electrode active material may be 80% by weight to 99% by weight, preferably 85% by weight to 99% by weight, more preferably 90% by weight to 99% by weight.

[0096] As the negative electrode current collector, a negative electrode current collector commonly used in the art may be used, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., and an aluminum-cadmium alloy may be used. The thickness of the negative electrode current collector is usually 3 μm to 500 μm, and similar to the positive electrode current collector, micro-protrusions and depressions may be formed on the surface of the current collector to improve the adhesion of the negative electrode active material. For example, the negative electrode current collector may be used in various shapes, such as a film, sheet, foil, net, porous body, foam body, non-woven fabric body, etc.

[0097] The conductive agent is used to provide conductivity to the negative electrode. Among them, any conductive agent may be used without particular limitation as long as it has electronic conductivity and does not cause chemical changes in the battery. Specific examples of the conductive agent may be graphite, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, pyrolytic carbon black, carbon fiber and carbon nanotube; metal powder or fiber, such as copper, nickel, aluminum and silver; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and any one of them or a mixture of two or more of them may be used. Based on the total weight of the negative electrode active material layer, the content of the conductive agent is usually 1% by weight to 30% by weight, preferably 1% by weight to 20% by weight, more preferably 1% by weight to 10% by weight.

[0098] The binder improves the adhesion between the negative electrode active material particles and the adhesion between the negative electrode active material and the negative electrode current collector. Specific examples of the binder may be: fluororesin binders, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders, including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber or styrene-isoprene rubber; cellulose binders, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose or regenerated cellulose; polyol binders, including polyvinyl alcohol; polyolefin binders, including polyethylene or polypropylene; polyimide binders; polyester binders; and silane binders, and any one of them or a mixture of two or more of them can be used. Based on the total weight of the negative electrode active material layer, the content of the binder may be 1% by weight to 30% by weight, preferably 1% by weight to 20% by weight, more preferably 1% by weight to 10% by weight.

[0099] (3) Separator

[0100] The separator separates the negative electrode from the positive electrode and provides a migration path for lithium ions. Among them, any separator can be used as this separator without particular limitation as long as it is usually used in lithium secondary batteries. Specifically, a porous polymer membrane, such as a porous polymer membrane prepared from polyolefin polymers (such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer), or a laminated structure having two or more layers can be used as the separator. In addition, conventional porous non-woven fabrics, such as non-woven fabrics formed from high-melting-point glass fibers or polyethylene terephthalate fibers, can be used. In addition, a coated separator containing a ceramic component or a polymer material can be used to ensure heat resistance or mechanical strength.

[0101] Cylindrical lithium secondary battery

[0102] Next, the cylindrical lithium secondary battery of the present invention will be described.

[0103] The cylindrical lithium secondary battery of the present invention includes: an electrode assembly obtained by winding a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate in one direction; a battery can for accommodating the electrode assembly; an electrolyte injected into the battery can; and a seal for sealing the open end of the battery can.

[0104] Preferably, the cylindrical lithium secondary battery of the present invention may be a large cylindrical battery having a form factor ratio (which is defined as the value obtained by dividing the diameter of the cylindrical battery by the height, that is, the ratio of the diameter (T) to the height (H)) of 0.4 or more. Here, the form factor refers to the value representing the diameter and height of the cylindrical battery.

[0105] For example, the cylindrical battery of the present invention can be 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 0.44), a 4880 cell (diameter 48 mm, height 80 mm, form factor ratio 0.600), a 4680 cell (diameter 46 mm, height 80 mm, form factor ratio 0.58), or a 4695 cell (diameter 46 mm, height 95 mm, form factor ratio 0.48). Among the numbers representing the form factor, the first two numbers represent the diameter of the cell, and the next two or three numbers represent the height of the cell.

[0106] Compared with the conventional case, the cylindrical lithium secondary battery of the present invention significantly reduces the gas generation amount. Therefore, excellent safety can be achieved even in cylindrical batteries with a form factor ratio of 0.4 to 0.6.

[0107] The cylindrical battery of the present invention can preferably be a battery with an earless structure that does not include electrode tabs, but is not limited thereto.

[0108] For example, a battery with an earless structure can have the following structure: the positive electrode plate and the negative electrode plate each include an uncoated portion where the active material layer is not formed. The uncoated portion of the positive electrode plate and the uncoated portion of the negative electrode plate are respectively disposed at the upper end and the lower end of the electrode assembly. The current collector plate is combined with the uncoated portion of the positive electrode plate and the uncoated portion of the negative electrode plate, and the current collector plate is connected to the electrode terminal.

[0109] Figure 3 The cross-sectional view of the cylindrical battery with an earless structure according to an embodiment of the present invention is shown. Hereinafter, the cylindrical battery according to an embodiment of the present invention will be described with reference to Figure 3 However, Figure 3 Only one embodiment of the present invention is shown, and the structure of the cylindrical battery of the present invention is not limited to the Figure 3 range disclosed in

[0110] The cylindrical battery 140 according to an embodiment of the present invention includes the electrode assembly 141 as described above, a battery can 142 that houses the electrode assembly 141, and a seal 143 that seals the open end of the battery can 142.

[0111] In this case, the positive electrode plate and the negative electrode plate of the electrode assembly can each include an uncoated portion where the active material layer is not formed, and can be stacked and wound such that the positive uncoated portion and the negative uncoated portion are respectively disposed at the upper end and the lower end of the electrode assembly. Since the electrode assembly has been described above, only the components other than the electrode assembly will be described hereinafter.

[0112] The battery can 142 is a cylindrical container with an upper opening, and it is formed of a conductive metal material such as aluminum or steel. The battery can accommodates the electrode assembly 141 in its internal space through the upper opening, and also accommodates an electrolyte (not shown) together.

[0113] Advantageously, the cylindrical battery 140 of the present invention does not include a current interruption device (CID).

[0114] (A) Electrolyte

[0115] The electrolyte used in the cylindrical lithium secondary battery of the present invention contains (i) a lithium salt, (ii) a non-aqueous organic solvent, and (iii) an additive, and a compound represented by Formula 1, a cyclic carbonate compound, and 1,3-propane sultone can be included as the (iii) additive.

[0116] [Formula 1]

[0117]

[0118] In Formula 1, n is an integer from 3 to 10.

[0119] (i) Lithium salt

[0120] The lithium salt is used as an electrolyte salt in a lithium secondary battery, and the lithium salt serves as a medium for transferring ions. Generally, for example, the lithium salt can contain Li + as a cation, and can contain a selection from F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 -, PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN - at least one selected from the group consisting of as an anion.

[0121] Specifically, the lithium salt may include a single material selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 , LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF2CF3)2 (lithium bis(perfluoroethanesulfonyl)imide, LiBETI), and LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), or a mixture of two or more thereof. In addition to these materials, lithium salts commonly used in electrolytes of lithium secondary batteries may be used without limitation.

[0122] The lithium salt may be included in the electrolyte at a concentration of 1.3 M or less. Specifically, the concentration is 1.2 M to 1.3 M. When the concentration of the lithium salt satisfies the above range, the electrolyte impregnation property of the electrode assembly having a core diameter of 5 mm or more can be improved.

[0123] (ii) Non-aqueous organic solvent

[0124] The non-aqueous organic solvent may include at least one selected from the group consisting of cyclic carbonate compounds, linear carbonate compounds, linear ester compounds, and cyclic ester compounds.

[0125] Specifically, the non-aqueous organic solvent may include cyclic carbonate compounds, linear carbonate compounds, or a mixture thereof.

[0126] Cyclic carbonate compounds are compounds with high viscosity and high dielectric constant, among which they can easily dissociate lithium salts in electrolytes. Specific examples of cyclic carbonate compounds may be at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate, among which cyclic carbonate compounds may include ethylene carbonate.

[0127] In the organic solvent, the content of cyclic carbonate compounds can be 15 vol% to 30 vol%, preferably 15 vol% to 25 vol%, and most preferably 15 vol% to 20 vol%. When the content of cyclic carbonate compounds is within the above range, the thermal safety can be improved by forming a uniform solid electrolyte interface (SEI) layer on the negative electrode plate.

[0128] In addition, linear carbonate compounds are compounds with low viscosity and low dielectric constant, among which typical examples of linear carbonate compounds may be at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, and linear carbonate compounds may specifically include ethyl methyl carbonate (EMC).

[0129] In addition, the non-aqueous organic solvent may also contain at least one ester compound selected from the group consisting of linear ester compounds and cyclic ester compounds to prepare an electrolyte with high ionic conductivity.

[0130] Specific examples of linear ester compounds may be at least one compound selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0131] In addition, cyclic ester compounds may include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0132] (iii) Additive

[0133] The electrolyte of the present invention may contain a compound represented by Formula 1, a cyclic carbonate compound, and 1,3-propane sultone as additives.

[0134] [Formula 1]

[0135]

[0136] In Formula 1, n is an integer from 3 to 10.

[0137] Specifically, in Formula 1, n can be an integer from 3 to 7.

[0138] When the integer n satisfies the above range, since the thermal properties of the compound itself can be improved, the stability of the film formed therefrom can be expected. If n in Formula 1 is less than 3, as the molecule becomes smaller and the amount of fluorine element decreases, while the boiling point decreases, the flame retardancy decreases, the high-temperature durability decreases, and at the same time it becomes vulnerable to electrochemical decomposition. Therefore, gas generation may occur during high-temperature storage, and the expansion characteristics are poor. In addition, when n in Formula 1 is greater than 8, as the fluorine element is excessively contained, the viscosity and non-polarity of the material increase, so the solubility in the electrolyte decreases, and thus the battery performance may be poor.

[0139] Preferably, the compound represented by Formula 1 may include at least one of the compounds represented by Formula 1-1 and 1-2.

[0140] [Formula 1-1]

[0141]

[0142] [Formula 1-2]

[0143]

[0144] The compound represented by Formula 1 can form a strong fluorine element-containing SEI film on the negative electrode surface, and at the same time, the double bond (C═C) functional group contained in its molecular structure causes an electrochemical reaction during the electrochemical decomposition reaction. In particular, since the compound represented by Formula 1 contains a fluoroalkyl group with excellent flame retardancy and non-combustibility in its molecular structure, it can form a passivation film on the positive electrode surface that can ensure excellent antioxidant properties, and at the same time can act as a radical scavenger caused by the fluorine element. Therefore, during the charge and discharge operations, since the side reaction between the electrode and the electrolyte is controlled, a lithium secondary battery with improved room temperature and low temperature life characteristics can be provided.

[0145] In particular, for the compound represented by Formula 1, free radicals are generated as the double bond of the acrylate is reductively decomposed, and while these free radicals promote the decomposition reaction of cyclic carbonate and / or 1,3-propane sultone (an additive to be described later), it can form a stronger SEI film.

[0146] Since in the compound represented by Formula 1 of the present invention, the acrylate functional group is connected to the terminal fluoroalkyl group via an ethylene group (-CH2-CH2-), compared with a compound in which the acrylate functional group is connected to the terminal fluoroalkyl group via a methylene group (-CH2-) (for example, 2,2,3,3,4,4,4-heptafluorobutyl acrylate), due to the increase in the molecular chain of the linking group, the flexibility is relatively high. Therefore, a film with more improved durability can be formed on the negative electrode surface.

[0147] In addition, as described above, since the compound represented by Formula 1 of the present invention contains two oxygen elements in its molecular structure and has a structural feature in which the acrylate functional group and the terminal fluoroalkyl group are connected (bonded) via an ethylene group (-CH2-CH2-), it not only forms a low-resistance and strong SEI on the electrode surface before side reactions occur to suppress the increase in interfacial resistance, but also prevents the exposure of the electrode surface, thereby suppressing side reactions between the electrode and the electrolyte. As a result, by effectively controlling the dissolution of transition metals from the positive electrode caused by film disintegration, the high-temperature stability can be improved, and thus a cylindrical lithium secondary battery capable of having excellent high-temperature storage characteristics and high-temperature cycle characteristics while reducing the battery swelling phenomenon can be achieved. For compounds containing more than three oxygen elements in their molecular structure, since this becomes a reason for reducing oxidation safety, there is a disadvantage of limited effects.

[0148] Based on the total amount of the electrolyte, the content of the compound represented by Formula 1 can be 0.5 wt% to 5.0 wt%, and more specifically, it can be 0.5 wt% to 3.0 wt%.

[0149] When the amount of the compound represented by Formula 1 satisfies the above range, by forming a stable film, the dissolution of transition metals from the positive electrode at high temperatures can be effectively suppressed, and thus excellent high-temperature durability can be achieved. That is, when the amount of the compound represented by Formula 1 is less than 0.5 wt%, since the film-forming effect is not significant, even during high-temperature storage, the SEI film will deteriorate, and thus an increase in resistance and a decrease in capacity may occur after high-temperature storage. In addition, when the amount of the compound represented by Formula 1 is greater than 5.0 wt%, since an overly thick film is formed during the initial charging process, the resistance increases, and thus deterioration of the output characteristics and initial capacity of the secondary battery may occur.

[0150] In addition to the compound represented by Formula 1, the electrolyte of the present invention may further contain a cyclic carbonate compound as an electrolyte additive. That is, since the compound represented by Formula 1 and the cyclic carbonate compound are used in combination as the electrolyte additive, when a film is formed by the reduction reaction of the cyclic carbonate compound, the radical chemical reaction generated by the compound represented by Formula 1 promotes the decomposition of the cyclic carbonate compound, and at the same time, a more stable film can be formed. Due to the synergistic effect of these two compounds, a stronger film can be formed, so that the high-temperature durability and capacity retention rate of the large cylindrical secondary battery can be effectively improved.

[0151] The cyclic carbonate compound may include vinylene carbonate, ethylene vinyl carbonate or a mixture thereof. When a mixture containing vinylene carbonate and ethylene vinyl carbonate is used as the cyclic carbonate compound, the weight ratio of vinylene carbonate to ethylene vinyl carbonate may be from 1:1 to 10:0.

[0152] In addition, the electrolyte of the present invention may contain 1,3-propane sultone as an additive to achieve the effect of enhancing the film on the electrode surface.

[0153] 1,3-Propane sultone can form a strong film on the surfaces of the positive electrode and the negative electrode. Since this film has excellent durability, additional side reactions between the electrode and the electrolyte can be inhibited, and an increase in resistance caused by the side reactions can be suppressed.

[0154] The electrolyte of the present invention may contain the compound of Formula 1, the cyclic carbonate compound and 1,3-propane sultone in a weight ratio of 1:0.5:0.2 to 1:20:10, specifically 1:0.5:0.2 to 1:10:8, and preferably 1:0.5:0.2 to 1:8:5.

[0155] When the content ratio of the additive satisfies the above range, a stronger SEI film and passivation film can be formed on the electrode surface, and at the same time, an appropriate amount of gas can be generated to control the internal pressure of the large cylindrical battery cell within a specific range. As a result, since the electrolyte impregnation property can be maximized, a cylindrical lithium secondary battery that can maintain high safety even at high output can be provided.

[0156] The non-aqueous electrolyte of the present invention may further contain other additives to prevent the disintegration of the negative electrode caused by the decomposition of the non-aqueous electrolyte in a high-output environment, or to further improve the low-temperature high-rate discharge characteristics, high-temperature stability, overcharge protection, and the effect of suppressing battery swelling at high temperatures.

[0157] Typical examples of these other additives may include at least one additive for SEI film formation, which is selected from the group consisting of halogenated carbonate compounds, sulfate / ester compounds, phosphate / ester compounds, borate / ester compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.

[0158] The halogenated carbonate compounds may include fluoroethylene carbonate (FEC).

[0159] The sulfate / ester compounds may include ethylene sulfite (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0160] The phosphate / ester compounds may include at least one compound selected from the group consisting of lithium difluoro(oxalato)phosphate, lithium difluorophosphate, tetramethyl trimethylsilyl phosphate, trimethylsilyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphite.

[0161] The borate / ester compounds may include tetraphenyl borate / ester, lithium oxalyl difluoroborate (LiODFB), and lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB).

[0162] The nitrile compounds may include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, hexanenitrile, heptanenitrile, cyclopentanenitrile, cyclohexanenitrile, 2-fluorobenzonitrile, 4-fluorobenzyl cyanide, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0163] The benzene compounds may include fluorobenzene, the amine compounds may include triethanolamine or ethylenediamine, and the silane compounds may include tetravinylsilane.

[0164] The lithium salt compounds are compounds different from the lithium salts contained in the non-aqueous electrolyte, and the lithium salt compounds may include lithium difluorophosphate (LiDFP), LiPO2F2, or LiBF4.

[0165] Two or more other additives can be mixed and used, and based on the total weight of the electrolyte, the content of these additives can be less than 10% by weight, particularly from 0.01% by weight or more to less than 8.0% by weight, and preferably from 0.05% by weight to 5.0% by weight. If the amount of other additives meets the above range, side reactions caused by unreacted additives can be suppressed, and the effects of improving the low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery can be further enhanced.

[0166] (B) Battery can

[0167] InFigure 3 In this case, the battery can 142 is electrically connected to the non-coated portion 146b of the negative electrode plate, and serves to contact an external power source to transfer the current applied from the external power source to the negative terminal of the negative electrode plate.

[0168] When necessary, a flange portion 147 and a crimping portion 148 may be included at the upper end of the battery can 142. The flange portion 147 may be formed by pressing the outer circumferential surface of the battery can 142 to a distance D1. The flange portion 147 prevents the electrode assembly 141 accommodated inside the battery can 142 from moving out through the upper end opening of the battery can 142, and can be used as a support for stably placing the seal body 143.

[0169] The crimping portion 148 may be formed on the upper portion of the flange portion 147, and has an extended and bent shape to surround the outer circumferential surface of the cover plate 143a provided on the flange portion 147 and a part of the upper surface of the cover plate 143a.

[0170] Next, the seal body 143 is used to seal the open end of the battery can 142. The seal body 143 includes a cover plate 143a and a first gasket 143b that provides airtightness and insulation between the cover plate 143a and the battery can 142. When necessary, it may also include a connection plate 143c that is electrically connected and mechanically coupled to the cover plate 143a. The cover plate 143a may be pressed onto the flange portion 147 formed in the battery can 142, and can be fixed by the crimping portion 148.

[0171] The cover plate 143a is a component formed of a conductive metal material. The cover plate 143a covers the upper end opening of the battery can 142. The cover plate 143a is electrically connected to the positive electrode plate of the electrode assembly 141, and is electrically insulated from the battery can 142 through the first gasket 143b. Therefore, the cover plate 143a can serve as the positive terminal of the cylindrical secondary battery. The cover plate 143a may include a protrusion 143d that protrudes upward from the center C, and the protrusion 143d may contact an external power source to allow current to be applied from the external power source.

[0172] The first gasket 143b may be disposed between the cover plate 143a and the crimping portion 148 to ensure the airtightness of the battery can 142 and electrically insulate the battery can 142 from the cover plate 143a.

[0173] When necessary, the cylindrical battery 140 of the present invention may further include current collector plates 144 and 145. The current collector plates are respectively joined to the non-coated portion 146a of the positive electrode plate and the non-coated portion 146b of the negative electrode plate, and are connected to the electrode terminals (i.e., the positive terminal and the negative terminal).

[0174] Specifically, the cylindrical battery 140 of the present invention may include a first current collector plate 144 joined to the upper portion of the electrode assembly 141 and a second current collector plate 145 joined to the lower portion of the electrode assembly 141.

[0175] It may also include the first current collector plate 144 and / or the second current collector plate 145.

[0176] The first current collector plate 144 is joined to the upper portion of the electrode assembly 141. The first current collector plate 144 is formed of a conductive metal material such as aluminum, copper, and nickel, and is electrically connected to the non-coated portion 146a of the positive electrode plate. A lead 149 may be connected to the first current collector plate 144. The lead 149 may extend upward from the electrode assembly 141 and may be joined to the connection plate 143c or may be directly joined to the lower surface of the cover plate 143a. The lead 149 and other components may be joined by welding. Preferably, the first current collector plate 144 may be integrally formed 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 collector plate 144.

[0177] The first current collector plate 144 is joined to the end of the non-coated portion 146a of the positive electrode plate, and the joining may be performed by methods such as laser welding, resistance welding, ultrasonic welding, and soldering, for example.

[0178] The second current collector plate 145 is joined to the lower portion of the electrode assembly 141. The second current collector plate 145 is formed of a conductive metal material such as aluminum, copper, and nickel, and is electrically connected to the non-coated portion 146b of the negative electrode plate. One surface of the second current collector plate 145 may be joined to the non-coated portion 146b of the negative electrode plate, and the other surface may be joined to the inner bottom surface of the battery can 142. In this case, the joining may be performed by methods such as laser welding, resistance welding, ultrasonic welding, and soldering.

[0179] When necessary, the cylindrical battery 140 of the present invention may further include an insulator 146. The insulator 146 may be provided to cover the upper surface of the first current collector plate 144. Since the insulator 146 covers the first current collector plate 144, direct contact between the first current collector plate 144 and the inner circumferential surface of the battery can 142 can be prevented.

[0180] The insulator 146 includes a lead hole 151 such that the lead 149 extending upward from the first current collector plate 144 can be led out. The lead 149 is led out upward through the lead hole 151 and joined to the lower surface of the connection plate 143c or the lower surface of the cover plate 143a.

[0181] The insulator 146 may be formed of an insulating polymer resin, for example, a polymer resin material such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

[0182] When necessary, the cylindrical battery 140 of the present invention may further include an exhaust portion 152 formed on the lower surface of the battery can 142. The exhaust portion 152 corresponds to a region on the lower surface of the battery can 142 where the thickness is thinner than that of the surrounding regions. Since the exhaust portion 152 is thinner, it is structurally weaker than the surrounding regions. Therefore, if the pressure in the cylindrical battery 140 increases above a certain level, the exhaust portion 152 ruptures, and the gas in the battery can 152 can be discharged to the outside to prevent the battery from exploding.

[0183] Figure 4 A cross-sectional view of a cylindrical battery with a tabless structure according to another embodiment of the present invention is shown. Hereinafter, the cylindrical battery according to another embodiment of the present invention will be described with reference to Figure 4 However, Figure 4 only one embodiment of the present invention is shown, and the structure of the cylindrical battery of the present invention is not limited to the Figure 4 range disclosed in

[0184] With reference to Figure 4 and compared with the cylindrical battery 140 shown in Figure 3 the cylindrical battery 170 according to another embodiment of the present invention has a different battery can and seal structure, and has substantially the same electrode assembly and electrolyte configuration.

[0185] Specifically, the cylindrical battery 170 includes a battery can 171, and a riveted terminal 172 is installed through the battery can 171. The riveted terminal 172 is installed on a partially enclosed closed surface (the upper surface in the figure) at one end of the battery can 171. The riveted terminal 172 is riveted to a through hole (the first opening at the first end) of the battery can 171, and an insulating second gasket 173 is provided therebetween. The riveted terminal 172 is exposed to the outside in a direction opposite to the direction of gravity.

[0186] The riveted terminal 172 includes a terminal exposed portion 172a and a terminal insertion portion 172b. The terminal exposed portion 172a is exposed to the outside of the closed surface of the battery can 171. The terminal exposed portion 172a may be located near the center of the partially enclosed surface of the battery can 171. The maximum diameter of the terminal exposed portion 172a may be formed to be larger than the maximum diameter of the through hole formed in the battery can 171. The terminal insertion portion 172b may be electrically connected to the non-coated portion 146a of the positive electrode plate through the center of the closed surface of the battery can 171. The terminal insertion portion 172b may be riveted to the inner surface of the battery can 171. That is, the end of the terminal insertion portion 172b may have a shape bent toward the inner surface of the battery can 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 can 171.

[0187] The lower end surface of the terminal insertion part 172b can be welded to the first current collector plate 144 connected to the non-coated part 146a of the positive electrode plate. An insulating cover 174 formed of an insulating material can be provided between the first current collector plate 144 and the inner surface of the battery can 171. The insulating cover 174 covers the upper part of the first current collector plate 144 and the upper edge part of the electrode assembly 141. Therefore, it can prevent a short circuit caused by contact between the outer peripheral non-coated part B3 of the electrode assembly 141 and the inner surface of the battery can 171 having a different polarity. The terminal insertion part 172b of the riveted terminal 172 can pass through the insulating cover 174 to be welded to the first current collector plate 144.

[0188] A second gasket 173 is provided between the battery can 171 and the riveted terminal 172 to prevent electrical contact between the battery can 171 and the riveted terminal 172 having opposite polarities to each other. Therefore, the upper surface of the battery can 171 having a substantially flat shape can function as the positive terminal of the cylindrical battery 170.

[0189] The second gasket 173 includes a gasket exposed part 173a and a gasket insertion part 173b. The gasket exposed part 173a is provided between the terminal exposed part 172a of the riveted terminal 172 and the battery can 171. The gasket insertion part 173b is provided between the terminal insertion part 172b of the riveted terminal 172 and the battery can 171. The gasket insertion part 173b can be tightly attached to the inner surface of the battery can 171 by being deformed together during the riveting process of the terminal insertion part 172b. For example, the second gasket 173 can be formed of a polymer resin having insulating properties.

[0190] The gasket exposed part 173a of the second gasket 173 can have an extended shape to cover the outer peripheral surface of the terminal exposed part 172a of the riveted terminal 172. In the case where the second gasket 173 covers the outer peripheral surface of the riveted terminal 172, a short circuit can be prevented during the process of joining an electrical connection component (such as a bus bar) to the upper surface of the battery can 171 and / or to the riveted terminal 172. Although not shown in the figure, the gasket exposed part 173a can have an extended shape that covers not only the outer peripheral surface of the terminal exposed part 172a but also a part of its upper surface.

[0191] In the case where the second gasket 173 is formed of a polymer resin, the second gasket 173 can be heat-melted and joined to the battery can 171 and the riveted terminal 172. In this case, the airtightness at the joining interface between the second gasket 173 and the riveted terminal 172 and at the joining interface between the second gasket 173 and the battery can 171 can be enhanced. In the case where the gasket exposed part 173a of the second gasket 173 has a shape extending to the upper surface of the terminal exposed part 172a, the riveted terminal 172 can be integrally joined to the second gasket 173 by insert injection molding.

[0192] The region 175 in the upper surface of the battery can 171 other than the regions occupied by the riveted terminal 172 and the second gasket 173 corresponds to the negative terminal having a polarity opposite to that of the riveted terminal 172.

[0193] The second current collector plate 176 is joined to the lower portion of the electrode assembly 141. The second current collector plate 176 is formed of a conductive metal material such as aluminum, steel, copper, and nickel, and is electrically connected to the non-coated portion 146b of the negative electrode plate.

[0194] Preferably, the second current collector plate 176 is electrically connected to the battery can 171. For this purpose, at least a part of the edge portion of the second current collector plate 176 may be disposed between the inner surface of the battery can 171 and the first gasket 178b, and thus be fixed. In one example, at least a part of the edge portion of the second current collector plate 176 may be fixed to the flange portion 180 by welding while being supported on the lower end surface of the flange portion 180 formed at the lower end of the battery can 171. In a variant example, at least a part of the edge portion of the second current collector plate 176 may be directly welded to the inner wall surface of the battery can 171.

[0195] The second current collector plate 176 may have a plurality of irregularities (not shown) formed radially on the surface facing the non-coated portion 146b. In the case of forming the irregularities, the second current collector plate 176 may be pressed to press the irregularities into the non-coated portion 146b.

[0196] Preferably, the second current collector plate 176 and the end portion of the non-coated portion 146b may be joined by welding, such as laser welding.

[0197] The seal 178 that seals the lower open end of the battery can 171 includes a cover plate 178a and a first gasket 178b. The first gasket 178b electrically isolates the cover plate 178a from the battery can 171. The crimping portion 181 fixes the edge of the cover plate 178a and the first gasket 178b together. The exhaust portion 179 is included in the cover plate 178a. The structure of the exhaust portion 179 is substantially the same as that of the above-described embodiment.

[0198] Preferably, the cover plate 178a is formed of a conductive metal material. However, since the first gasket 178b is disposed between the cover plate 178a and the battery can 171, the cover plate 178a does not have an electrode polarity. The seal 178 serves to seal the lower open end of the battery can 171 and discharge gas when the internal pressure of the battery cell 170 increases above a critical value.

[0199] Preferably, the riveting terminal 172 electrically connected to the non-coated portion 146a of the positive electrode plate is used as the positive electrode terminal. In addition, a portion 175 of the upper surface of the battery can 171 other than the riveting terminal 172 is electrically connected to the non-coated portion 146b of the negative electrode plate through the second current collector plate 176 and serves as the negative electrode terminal. As described above, when the two electrode terminals are provided on the upper portion of the cylindrical battery, electrical connection components such as bus bars can be provided only on one side of the cylindrical battery 170. This can simplify the battery pack structure and improve the energy density. In addition, since the portion 175 serving as the negative electrode terminal has a substantially flat shape, a sufficient bonding area can be ensured to bond electrical connection components such as bus bars. Therefore, the cylindrical battery 170 can reduce the resistance at the joint portion of the electrical connection component to a desired level.

[0200] In the case of forming the cylindrical lithium secondary battery having the above-described earless structure, since the battery having the earless structure has a smaller current concentration than the conventional battery having electrode ears, heat generation in the battery can be effectively reduced. Therefore, an effect of improving the thermal stability of the battery can be obtained.

[0201] The cylindrical lithium secondary battery of the present invention as described above can be used to prepare a battery pack. Figure 6 The configuration of the battery pack according to an embodiment of the present invention is schematically shown. Referring to Figure 6 , the battery pack 3 according to an embodiment of the present invention includes: an assembly formed by electrically connecting cylindrical secondary batteries 1, and a battery pack case 2 that houses the assembly. The cylindrical secondary battery 1 is the single battery of the above-described embodiment. In the drawings, for the sake of convenience of explanation, components such as bus bars for electrically connecting the cylindrical secondary battery 1, the cooling unit, and the external terminals are omitted.

[0202] The battery pack 3 can be installed in a vehicle. For example, the vehicle can be an electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. The vehicle includes a four-wheel vehicle or a two-wheel vehicle.

[0203] Hereinafter, the present invention will be described in more detail based on specific examples.

[0204] Example 1

[0205] (Preparation of electrolyte)

[0206] LiPF6 was dissolved in a non-aqueous organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 such that the concentration of LiPF6 was 1.3 M. Then, 0.5 wt% of the compound represented by Formula 1-2, 2.0 wt% of vinylene carbonate (VC), 1.0 wt% of 1,3-propane sultone (PS), and 0.2 wt% of adiponitrile (AD), 0.2 wt% of succinonitrile, and 0.3 wt% of lithium difluorophosphate (hereinafter referred to as "LiDFP") as other additives were added thereto to prepare an electrolyte (see Table 1 below).

[0207] (Preparation of secondary battery)

[0208] The positive electrode active material in the form of single particles and having a unimodal particle size distribution with an average particle size D 50 of 3 μm (Li[Ni 0.9 Co 0.06 Mn 0.03 Al 0.01 O2), carbon nanotubes, and a PVDF binder were added to N-methylpyrrolidone in a weight ratio of 97.8:0.6:1.6 and mixed to prepare a positive electrode paste. One surface of an aluminum current collector was coated with the positive electrode paste, dried at 120 °C, and then roll-pressed to prepare a positive electrode plate.

[0209] The negative electrode active material (weight ratio of graphite to SiO = 95:5), a conductive agent (super C), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were added to water in a weight ratio of 96:2:1.5:0.5 and mixed to prepare a negative electrode paste. One surface of a copper current collector was coated with the negative electrode paste, dried at 150 °C, and then roll-pressed to prepare a negative electrode plate.

[0210] A separator was disposed between the positive electrode plate and the negative electrode plate prepared above, and they were stacked in the order of separator / positive electrode plate / separator / negative electrode plate and then wound to prepare an electrode assembly (core part diameter: 7 mm). The electrode assembly prepared as described above was inserted into a cylindrical battery can, and then an electrolyte was injected to prepare a 4680 battery cell (form factor ratio: 0.58).

[0211] Example 2

[0212] (Preparation of electrolyte)

[0213] LiPF6 was dissolved in a non-aqueous organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 such that the concentration of LiPF6 was 1.3 M. Then, 1.0 wt% of the compound represented by Formula 1-2, 2.0 wt% of vinylene carbonate (VC), 1.0 wt% of 1,3-propane sultone (PS), and 0.2 wt% of adiponitrile (AD), 0.2 wt% of succinonitrile, and 0.3 wt% of LiDFP as other additives were added thereto to prepare an electrolyte (see Table 1 below).

[0214] (Preparation of secondary battery)

[0215] A 4680 battery cell (shape factor ratio: 0.58) was prepared in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0216] Example 3

[0217] LiPF6 was dissolved in a non-aqueous organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 such that the concentration of LiPF6 was 1.3 M. Then, 3.0 wt% of the compound represented by Formula 1-2, 3.0 wt% of vinylene carbonate (VC), 1.0 wt% of 1,3-propane sultone (PS), and 0.2 wt% of adiponitrile (AD), 0.2 wt% of succinonitrile, and 0.3 wt% of LiDFP as other additives were added thereto to prepare an electrolyte (see Table 1 below).

[0218] (Preparation of secondary battery)

[0219] A 4680 battery cell (shape factor ratio: 0.58) was prepared in the same manner as in Example 1, except that the electrolyte prepared above was injected.

[0220] Example 4

[0221] LiPF6 was dissolved in a non-aqueous organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 such that the concentration of LiPF6 was 1.3 M. Then, 3.0 wt% of the compound represented by Formula 1-2, 4.5 wt% of vinylene carbonate (VC), 3.0 wt% of 1,3-propane sultone (PS), and 0.2 wt% of adiponitrile (AD), 0.2 wt% of succinonitrile, and 0.3 wt% of LiDFP as other additives were added thereto to prepare an electrolyte (see Table 1 below).

[0222] (Preparation of secondary battery)

[0223] Prepare a 4680 battery cell (shape factor ratio: 0.58) in the same manner as in Example 1, except that the electrolyte prepared above is injected.

[0224] Comparative Example 1

[0225] Dissolve LiPF6 in a non-aqueous organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 such that the concentration of LiPF6 is 1.3 M, and then add 2.0 wt% of vinylene carbonate (VC), 1.0 wt% of 1,3-propane sultone (PS), and 0.2 wt% of adiponitrile (AD), 0.2 wt% of succinonitrile, and 0.3 wt% of LiDFP as other additives to prepare an electrolyte (see Table 1 below).

[0226] (Prepare secondary battery)

[0227] Prepare a 4680 battery cell (shape factor ratio: 0.58) in the same manner as in Example 1, except that the electrolyte prepared above is injected.

[0228] Comparative Example 2

[0229] Dissolve LiPF6 in a non-aqueous organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 such that the concentration of LiPF6 is 1.3 M, and then add 0.1 wt% of the compound represented by Formula 1-2, 2.0 wt% of vinylene carbonate (VC), 1.0 wt% of 1,3-propane sultone (PS), and 0.2 wt% of adiponitrile (AD), 0.2 wt% of succinonitrile, and 0.3 wt% of LiDFP as other additives to prepare an electrolyte (see Table 1 below).

[0230] (Prepare secondary battery)

[0231] Prepare a 4680 battery cell (shape factor ratio: 0.58) in the same manner as in Example 1, except that the electrolyte prepared above is injected.

[0232] Comparative Example 3

[0233] Dissolve LiPF6 in a non-aqueous organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 such that the concentration of LiPF6 is 1.3 M. Then, add 1.0 wt% of the compound represented by Formula 1-2, 2.0 wt% of vinylene carbonate (VC), 0.1 wt% of 1,3-propane sultone (PS), and 0.2 wt% of adiponitrile (AD), 0.2 wt% of succinonitrile, and 0.3 wt% of LiDFP as other additives to prepare an electrolyte (see Table 1 below).

[0234] (Preparation of secondary battery)

[0235] Prepare a 4680 battery cell (form factor ratio: 0.58) in the same manner as in Example 1, except that the electrolyte prepared above is injected.

[0236] Comparative Example 4

[0237] Dissolve LiPF6 in a non-aqueous organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 such that the concentration of LiPF6 is 1.3 M. Then, add 0.3 wt% of the compound represented by Formula 1-2, 2.0 wt% of vinylene carbonate (VC), 4.5 wt% of 1,3-propane sultone (PS), and 0.2 wt% of adiponitrile (AD), 0.2 wt% of succinonitrile, and 0.3 wt% of LiDFP as other additives to prepare an electrolyte (see Table 1 below).

[0238] (Preparation of secondary battery)

[0239] Prepare a 4680 battery cell (form factor ratio: 0.58) in the same manner as in Example 1, except that the electrolyte prepared above is injected.

[0240] Comparative Example 5

[0241] Dissolve LiPF6 in a non-aqueous organic solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 such that the concentration of LiPF6 is 1.3 M. Then, add 5.5 wt% of the compound represented by Formula 1-2, 2.0 wt% of vinylene carbonate (VC), 1.0 wt% of 1,3-propane sultone (PS), and 0.2 wt% of adiponitrile (AD), 0.2 wt% of succinonitrile, and 0.3 wt% of LiDFP as other additives to prepare an electrolyte (see Table 1 below).

[0242] (Preparation of secondary battery)

[0243] Prepare a 4680 battery cell (shape factor ratio: 0.58) in the same manner as in Example 1, except that the electrolyte prepared above is injected.

[0244] Comparative Example 6

[0245] (Prepare a secondary battery)

[0246] Insert the electrode assembly prepared in Example 1 (core part diameter: 7 mm) into a cylindrical battery can, and then inject the electrolyte prepared in Example 1 to prepare a 21700 battery cell (shape factor ratio: 0.03).

[0247] [Table 1]

[0248]

[0249] [Experimental Example]

[0250] Experimental Example 1. Evaluation of gas generation amount

[0251] Charge each of the battery cells prepared in Example 1 and Comparative Example 1 at a constant current-constant voltage with a C-rate of 0.33C to 4.0V at room temperature and discharge at a C-rate of 0.2C to 2.5V to activate each battery cell. Subsequently, collect the gas in the battery cell, and then measure the gas generation amount by gas chromatography-mass spectrometry (GC-MS) analysis (BG-10).

[0252] Set the gas generation amount of Comparative Example 1 to 100%, and calculate the volume change rate of Example 1 as a value relative to Comparative Example 1. The values are shown in Table 2 below.

[0253] [Table 2]

[0254] Gas generation amount (%) Example 1 82.0 Comparative Example 1 100.0

[0255] Referring to Table 2, it can be confirmed that, compared with the battery cell of Example 1, although the total additive content is higher than that of Comparative Example 1, the gas generation amount in the battery cell is reduced.

[0256] Experimental Example 2. Evaluation of initial capacity and initial resistance

[0257] (1) Evaluation of initial discharge energy (Wh)

[0258] Charge each of the battery cells prepared in Examples 1 to 4 and Comparative Examples 2, 4, and 5 at a constant current-constant voltage with a C-rate of 0.33C to 4.0V at room temperature, and then discharge at a C-rate of 0.2C to 2.5V to measure the discharge energy, and the results are shown in Table 3 below.

[0259] (2) Evaluation of initial DC resistance

[0260] The respective battery cells prepared in Examples 1 to 4 and Comparative Examples 2, 4, and 5 were charged at a constant current-constant voltage at a C rate of 0.33C to a state of charge (SOC) of 50% at room temperature. Then, when the battery cells were discharged at a C rate of 0.5C for 10 seconds at SOC 50%, the initial DC resistance was calculated using the voltage difference, and the results are shown in Table 3 below.

[0261] [Table 3]

[0262] Initial discharge energy Initial DC resistance Example 1 101.13 95.23 Example 2 100.92 95.61 Example 3 100.82 95.99 Example 4 100.10 98.78 Comparative Example 2 99.90 99.48 Comparative Example 4 97.85 104.48 Comparative Example 5 98.1 110.5

[0263] As shown in Table 3, for the battery cells of Examples 1 to 4, it was confirmed that the initial discharge energy was improved and the initial resistance was significantly reduced compared to the battery cells of Comparative Examples 2, 4, and 5.

[0264] Based on these results, in the case of containing three additives in a specific composition ratio, it was confirmed that the electrolyte impregnation property was improved due to controlling the gas generation to reduce the internal pressure of the battery cell, and thus the initial resistance was reduced.

[0265] Experimental Example 3. Discharge Capacity Relative to C Rate

[0266] The respective battery cells prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were charged at a constant current-constant voltage at a C rate of 0.33C to 4.2V at room temperature, and then the battery cells were discharged to 2.5V while changing the current to C rates of 1C and 2C, whereby the discharge capacity retention rate was calculated, and the results are shown in Table 4 below.

[0267] [Table 4]

[0268]

[0269] As shown in Table 4, for the battery cells of Examples 1 to 4, it was understood that the discharge capacity retention rate was improved for all compared to the battery cells of Comparative Examples 1 to 5.

[0270] Experimental Example 4. Evaluation of High-Temperature Cycle Capacity Retention Rate

[0271] The respective battery cells prepared in Examples 1 to 3 and Comparative Examples 2 to 6 were charged at a constant current-constant voltage at a C rate of 0.33C to 4.2V at room temperature (25°C) and then discharged to 2.5V at a C rate of 0.2C, and then the initial capacity was measured. Subsequently, at a high temperature (40°C), they were charged at a constant current-constant voltage at a C rate of 0.33C to 4.2V and then discharged to 2.5V at a C rate of 0.2C. The above was set as one cycle, and charging and discharging were performed for 100 cycles. The capacity retention rate with respect to the initial capacity after 1 cycle after 100 cycles at 40°C was measured, and the results are shown in Table 5 below.

[0272] [Table 5]

[0273] Capacity retention rate after 100 cycles (%) Example 1 101.66 Example 2 101.56 Example 3 101.52 Comparative Example 2 99.67 Comparative Example 3 90.22 Comparative Example 4 100.55 Comparative Example 5 87.75 Comparative Example 6 88.50

[0274] As shown in Table 5, for the battery cells of Examples 1 to 3, it can be understood that the high-temperature cycle capacity retention rate is improved in all cases compared with the battery cells of Comparative Examples 2 to 6.

[0275] In particular, for the battery cell of Comparative Example 6 with a different shape factor, in the case of using an electrolyte solution with the same additive composition, since it is difficult to control the internal pressure of the battery cell and the electrolyte impregnation property is reduced, it can be understood that the high-temperature cycle capacity retention rate is significantly reduced compared with the battery cells of Examples 1 to 3.

[0276] Experimental Example 5. Thermal Stability Evaluation

[0277] While heating each of the battery cells prepared in Examples 1 to 3 and Comparative Examples 1 to 6 at a rate of 2 °C per minute, the ignition temperature was measured. In this case, the ignition temperature of Comparative Example 1 was set to "0", and the ignition temperature values of the battery cells of Examples 1 to 3 and Comparative Examples 2 to 6 were calculated as values relative to the battery cell of Comparative Example 1, and the results are shown in Table 6 below.

[0278] [Table 6]

[0279] Ignition temperature (°C) Example 1 +10 Example 2 +12 Example 3 +14 Comparative Example 1 0 Comparative Example 2 0 Comparative Example 3 +3 Comparative Example 4 +1 Comparative Example 5 +4 Comparative Example 6 +5

[0280] As shown in Table 6, for the battery cells of Examples 1 to 3, since the stability is improved with the improvement of the electrolyte impregnation property, it can be understood that ignition occurs at a higher temperature compared with the battery cells of Comparative Examples 1 to 6.

[0281] Reference numeral

[0282] 10: Positive electrode plate

[0283] 11: Negative electrode plate

[0284] 12: Separator

[0285] 20: Current collector

[0286] 21, 21a: Active material layer

[0287] 22, 22a, 22c, 146b: Non-coated part

[0288] 24: Insulating layer

[0289] 140, 170: Cylindrical battery

[0290] 141: Electrode assembly

[0291] 142, 171: Battery can

[0292] 143, 178: Sealing body

[0293] 144: First current collector plate

[0294] 145, 176: Second current collector plate

[0295] 146a: Non-coated part of the positive electrode plate

[0296] 146b: Non-coated part of the negative electrode plate

[0297] 146: Insulator

[0298] 152: Exhaust part

[0299] 172: Riveting terminal

[0300] 173: Second gasket

[0301] 173a: Gasket exposed part

[0302] 173b: Gasket insertion part

[0303] 147, 180: Circular edge part

[0304] 148: Crimping part

[0305] 149: Lead wire

[0306] 172a: Terminal exposed part

[0307] 173b: Terminal insertion part

[0308] 174: Insulating cover

[0309] 178b: First gasket

[0310] 180: Circular edge part

Claims

1. A cylindrical lithium secondary battery, comprising: An electrode assembly, wherein a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate are wound in one direction; A battery can, which houses the electrode assembly; An electrolyte injected into the battery can; and A sealing body that seals an open end of the battery can, Among them, The positive electrode plate and the negative electrode plate each include an uncoated portion where an active material layer is not formed, and each has the following structure: at least a part of the uncoated portion of the positive electrode plate or the negative electrode plate defines an electrode tab; The form factor ratio of the cylindrical lithium secondary battery is 0.4 or more, The diameter of the core portion of the electrode assembly is 5 mm to 8 mm; and The electrolyte includes a lithium salt, a non-aqueous organic solvent, and an additive, Wherein, the additive includes a compound represented by Formula 1, a cyclic carbonate compound, and 1,3-propane sultone, Based on the total amount of the electrolyte, the content of the compound represented by Formula 1 is 0.5 wt% to 5.0 wt%; The weight ratio of the compound represented by Formula 1, the cyclic carbonate compound, and 1,3-propane sultone is 1:0.5:0.2 to 1:20:10; [Formula 1] Wherein, in Formula 1, n is an integer from 3 to 10.

2. The cylindrical lithium secondary battery according to claim 1, wherein, The positive electrode plate includes a positive electrode active material in which the amount of nickel (Ni) among metal elements other than lithium is 80 mol% or more.

3. The cylindrical lithium secondary battery according to claim 2, wherein, The positive electrode active material is a lithium nickel-based oxide represented by Formula 2, [Formula 2] Li a Ni b Co c M 1 d M 2 e O2 Wherein, in Formula 2, M 1 is manganese (Mn), aluminum (Al), or a combination thereof, M 2 is at least one selected from zirconium (Zr), tungsten (W), yttrium (Y), barium (Ba), calcium (Ca), titanium (Ti), magnesium (Mg), tantalum (Ta), and niobium (Nb), and 0.8 ≤ a ≤ 1.2, 0.85 ≤ b < 1, 0 < c < 0.15, 0 < d < 0.15, and 0 ≤ e ≤ 0.

1.

4. The cylindrical lithium secondary battery according to claim 1, wherein, The positive electrode plate includes a positive electrode active material composed of single particles, quasi-single particles, and / or a combination thereof.

5. The cylindrical lithium secondary battery according to claim 1, wherein, The negative electrode plate includes a silicon-based negative electrode active material and a carbon-based negative electrode active material.

6. The cylindrical lithium secondary battery according to claim 5, wherein, The silicon-based negative electrode active material and the carbon-based negative electrode active material are included in a weight ratio of 1:99 to 20:

80.

7. The cylindrical lithium secondary battery according to claim 1, wherein, The form factor ratio of the cylindrical lithium secondary battery is 0.4 to 0.

6.

8. The cylindrical lithium secondary battery according to claim 1, wherein, The cylindrical lithium secondary battery is a 46110 cell, a 48110 cell, a 4880 cell, a 4680 cell, or a 4695 cell.

9. The cylindrical lithium secondary battery according to claim 1, wherein, The concentration of the lithium salt is 1.2 M to 1.3 M.

10. The cylindrical lithium secondary battery according to claim 1, wherein, In Formula 1, n is an integer from 3 to 7.

11. The cylindrical lithium secondary battery according to claim 1, wherein, Based on the total amount of the electrolyte, the content of the compound represented by Formula 1 is 0.5 wt% to 3.0 wt%.

12. The cylindrical lithium secondary battery according to claim 1, wherein, The cyclic carbonate compound includes vinylene carbonate, ethyl vinyl carbonate, or a mixture thereof.

13. The cylindrical lithium secondary battery according to claim 1, wherein, The weight ratio of the compound of Formula 1, the cyclic carbonate compound, and 1,3-propane sultone is 1:0.5:0.2 to 1:10:

8.

14. The cylindrical lithium secondary battery according to claim 1, wherein, The uncoated portion of the positive electrode plate and the uncoated portion of the negative electrode plate are formed on one side of the positive electrode plate and the negative electrode plate respectively along the winding direction of the electrode assembly, A current collector plate is joined to each of the uncoated portion of the positive electrode plate and the uncoated portion of the negative electrode plate, and The current collector plate is connected to an electrode terminal.

15. The cylindrical lithium secondary battery according to claim 14, wherein, The uncoated portions of the positive electrode plate and the negative electrode plate are processed into a form of a plurality of independently bendable sections, and At least a part of the plurality of sections bends toward the winding center of the electrode assembly.

16. The cylindrical lithium secondary battery according to claim 15, wherein, At least a part of the plurality of sections overlap at the upper and lower ends of the electrode assembly, and The current collector plate is joined to the overlapping plurality of sections.

17. The cylindrical lithium secondary battery according to claim 14, wherein, An insulating layer is further formed on the positive electrode plate in a direction parallel to the winding direction, and the insulating layer covers a part of the positive electrode active material layer and a part of the non-coated portion.

18. A battery pack, comprising the cylindrical lithium secondary battery according to any one of claims 1 to 17.

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