Lithium-ion rechargeable battery

Abstract

The object of the present invention is to provide a lithium secondary battery that can achieve excellent thermal stability even when the volume of a can-type battery is increased by using single particles or pseudo-single particles as a positive electrode active material. The present invention relates to a secondary battery including an electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive and negative electrode plates are wound in one direction, a battery can in which the electrode assembly is housed, and a sealing body that seals the open end of the battery can. The positive electrode plate includes a positive electrode active material including single particles, pseudo-single particles, or a combination thereof, and the D of the positive electrode active material is min is 1.0 μm or more.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0136711 filed on October 14, 2021 and Korean Patent Application No. 10-2022-0121172 filed on September 23, 2022, and all the contents disclosed in the documents of the Korean patent applications are incorporated herein by reference in their entirety.

[0002] The present invention relates to a lithium secondary battery, and more specifically, to a lithium secondary battery capable of achieving excellent thermal stability even when the volume increases by applying single particles and / or pseudo-single particle positive electrode active materials.

Background Art

[0003] With the development of technologies such as electric vehicles and portable electronic devices, the demand for lithium secondary batteries as an energy source has been rapidly increasing.

[0004] Lithium secondary batteries can be divided into can-type batteries such as cylindrical or prismatic batteries and pouch-type batteries according to the material of the battery case. A can-type battery is manufactured by housing a jelly-roll type electrode assembly, which is manufactured by sequentially laminating a sheet-shaped positive electrode plate, a separator, and a negative electrode plate in a battery can and then winding it in one direction, and then covering and sealing a cap plate on the upper part of the battery can. The positive electrode plate and the negative electrode plate are each provided with strip-shaped positive electrode tabs and negative electrode tabs, and the positive electrode tabs and the negative electrode tabs are connected to electrode terminals and electrically connected to an external power source. For reference, the positive electrode terminal is the cap plate, and the negative electrode terminal is the battery can. However, in the case of a conventional can-type battery having such a structure, there is a problem that current concentrates on the strip-shaped electrode tabs, resulting in high resistance, a large amount of heat generation, and poor current collection efficiency.

[0005] On the other hand, with the recent advancements in electric vehicle technology, the need for high-capacity batteries is increasing, necessitating the development of larger, bulkier can-type batteries. Conventionally, with the small can-type batteries commonly used, such as the 1865 and 2170 form factors, the small capacity meant that resistance and heat generation did not significantly affect battery performance. However, applying the specifications of conventional small can-type batteries directly to larger can-type batteries could lead to serious battery safety issues.

[0006] As battery size increases, the amount of heat and gas generated inside the battery also increases. This heat and gas can raise the internal temperature and pressure of the battery, potentially causing it to ignite or explode. To prevent this, the heat and gas inside the battery must be properly dissipated to the outside. For this to happen, the cross-sectional area of ​​the battery, which serves as a passage for heat to escape, needs to increase in proportion to the increase in volume. However, the increase in cross-sectional area is usually less than the increase in volume. Therefore, as batteries become larger, the amount of heat generated inside the battery increases, which increases the risk of explosion and can lead to problems such as reduced output. Furthermore, when performing rapid charging at high voltage, a large amount of heat can be generated around the electrode tabs in a short time, potentially causing the battery to ignite.

[0007] Therefore, in order to achieve high capacity, there is a need to develop can-type batteries that have a large volume and high safety. [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to solve the above-mentioned problems and to provide a lithium secondary battery that can achieve excellent thermal stability even when the volume of the can-type battery increases, by applying single particles or pseudo-single particles as the positive electrode active material. [Means for solving the problem]

[0009] According to one embodiment, the present invention provides a secondary battery including a positive electrode plate, a negative electrode plate, an electrode assembly in which a separator interposed between the positive electrode plate and the negative electrode plate is wound in one direction, a battery can in which the electrode assembly is housed, and a sealing body that seals an open end of the battery can. The positive electrode plate includes a positive electrode active material including single particles, pseudo-single particles, or a combination thereof, and the D min of the positive electrode active material is 1.0 μm or more, and a cylindrical lithium secondary battery is provided.

[0010] Further, the positive electrode active material may include a lithium nickel-based oxide containing 80 mol% or more of Ni with respect to the total number of moles of transition metals, and for example, may include a lithium nickel-based oxide represented by the following [Chemical Formula 1]. [Chemical Formula 1] Li a Ni b Co c M 1 d M 2 e O2

[0011] In the Chemical Formula 1, M 1 is Mn, Al, or a combination thereof, and M 2 is Zr, W, Ti, Mg, Ca, Sr, and Ba, and 0.8 ≦ a ≦ 1.2, 0.83 ≦ b < 1, 0 < c < 0.17, 0 < d < 0.17, 0 ≦ e ≦ 0.1.

[0012] On the other hand, the negative electrode plate may include a silicon-based negative electrode active material.

[0013] Further, the negative electrode plate may include a silicon-based negative electrode active material and a carbon-based negative electrode active material, and here, the silicon-based negative electrode active material and the carbon-based negative electrode active material may be included in a weight ratio of 1:99 to 20:80.

[0014] On the other hand, the secondary battery can be a cylindrical battery with a form factor ratio of 0.4 or more, for example, a 46110 cell, a 4875 cell, a 48110 cell, a 4880 cell, or a 4680 cell. Here, the form factor ratio is the value obtained by dividing the diameter of the cylindrical battery by its height.

[0015] Furthermore, the secondary battery according to the present invention may be a battery in which the positive electrode plate and the negative electrode plate each include a blank portion on which no active material layer is formed, and at least a part of the blank portion of the positive electrode plate or the negative electrode plate defines an electrode tab.

[0016] The blank portions of the positive and negative electrode plates are respectively located along the ends of one side of the positive and negative electrode plates parallel to the winding direction of the electrode assembly, and a current collector plate is attached to each of the blank portions of the positive and negative electrode plates, and the current collector plate can be connected to the electrode terminals.

[0017] On the other hand, the blank portion of the positive electrode plate and the blank portion of the negative electrode plate are processed into a plurality of independently bendable segmented pieces, and at least a portion of the plurality of segmented pieces may define the electrode tab and be bent toward the winding center C of the electrode assembly. Furthermore, at least a portion of the bent plurality of segmented pieces may overlap on the upper and lower ends of the electrode assembly, and the current collector plate may be bonded to the overlapping plurality of segmented pieces.

[0018] On the other hand, an insulating layer can be further formed on the positive electrode plate, covering a portion of the positive electrode active material layer and a portion of the blank area in a direction parallel to the winding direction.

[0019] According to other embodiments, the present invention provides a battery pack including the lithium secondary battery according to the present invention, and an automobile including the battery pack. [Effects of the Invention]

[0020] The lithium secondary battery according to the present invention uses a positive electrode active material consisting of single particles and / or pseudo-single particles as the positive electrode active material, thereby minimizing the generation of gas due to particle cracking during electrode manufacturing and internal cracking during charging and discharging, and thus achieving excellent safety even in large batteries with increased volume.

[0021] Furthermore, the lithium secondary battery according to the present invention is D min By using a positive electrode active material with a minimum particle size (D) of 1.0 μm or larger, the thermal stability of the battery can be further improved. Our research has shown that even when single particles and / or pseudo-single particles are used as the positive electrode active material, the effect of suppressing particle cracking and improving thermal stability after rolling differs depending on the particle size of the positive electrode active material. In particular, when the positive electrode active material contains particles with a particle size of less than 1.0 μm, the linear pressure increases during the rolling process, leading to increased particle cracking and reduced thermal stability. Therefore, when applied to large cylindrical batteries, sufficient thermal stability could not be ensured. Accordingly, in this invention, the minimum particle size (D) is used. min By using a positive electrode active material in which the ) is controlled to 1.0 μm or more, the effect of improving thermal stability can be maximized.

[0022] Furthermore, the lithium secondary battery according to the present invention is D 50 , D max Furthermore, by applying a cathode active material with appropriately adjusted particle size distribution (PSD), the increase in resistance due to the application of single particles is minimized, thereby enabling the realization of excellent capacitance and power characteristics.

[0023] Furthermore, the lithium secondary battery according to the present invention can include a silicon-based negative electrode active material with a large capacity as the negative electrode active material, in which case a higher energy density can be achieved.

[0024] Furthermore, the lithium secondary battery according to the present invention can have a structure in which the blank portions of the positive and negative electrode plates serve as electrode tabs, for example, a tab-less structure. Conventional batteries have a structure in which the electrode plates and electrode leads are connected via electrode tabs, but in this case, a large amount of current concentrates on the electrode tabs during charging, generating a lot of heat around the electrode tabs. In particular, this phenomenon worsens during rapid charging, and there is a risk of the battery igniting or exploding. In contrast, the lithium secondary battery according to the present invention can be formed in a structure in which blank portions without an active material layer are formed at the ends of the positive and negative electrode plates, and these blank portions are connected to the electrode terminals by welding them to a current collector plate having a wide cross-sectional area. Since batteries with such a structure have less current concentration compared to conventional batteries with electrode tabs, the heat generated inside the battery can be effectively reduced, thereby improving the thermal stability of the battery. [Brief explanation of the drawing]

[0025] [Figure 1] This figure shows the stacked state of the electrode assembly according to the present invention before winding. [Figure 2] This is a cross-sectional view showing the structure of the electrode plate of an electrode assembly according to one embodiment of the present invention. [Figure 3] This is a cross-sectional view showing the structure of a tablet-type battery according to one embodiment of the present invention. [Figure 4] This is a cross-sectional view showing the structure of a tablet-type battery according to another embodiment of the present invention. [Figure 5] This is a diagram illustrating the structure of an electrode assembly according to one embodiment of the present invention. [Figure 6] This is a diagram illustrating the battery pack according to the present invention. [Figure 7] This is a diagram illustrating an automobile including a battery pack according to the present invention. [Figure 8] This is an SEM image of the positive electrode active material used in Example 1. [Figure 9] This is an SEM image of the positive electrode active material used in Example 2. [Figure 10] This is an SEM image of the positive electrode active material used in Comparative Example 2. [Figure 11] This graph shows the hotbox test results for 4680 cells produced using Sample 1 of Example 1 and Comparative Example 1. [Figure 12] This graph shows the hotbox test results for 4680 cells from Samples 2 and 3 of Example 1, Samples 1 and 2 of Example 2, and Comparative Example 2. [Figure 13] This is a cross-sectional SEM image of the positive electrode plate manufactured in Example 1. [Figure 14] This is a cross-sectional SEM image of the positive electrode plate manufactured in Comparative Example 1. [Modes for carrying out the invention]

[0026] The present invention will be described in more detail below.

[0027] The terms and words used herein and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0028] In this invention, "primary particle" refers to a particle unit in which no grain boundaries are visible when observed at a field of view of 5,000x to 20,000x using a scanning electron microscope or electron backscatter diffraction (EBSD) pattern analyzer. "Average particle size of primary particles" refers to the arithmetic mean calculated after measuring the particle sizes of primary particles observed with a scanning electron microscope or EBSD image.

[0029] In this invention, a "secondary particle" is a particle formed by the aggregation of multiple primary particles. In this invention, in order to distinguish it from conventional secondary particles formed by the aggregation of tens to hundreds of primary particles, secondary particles formed by the aggregation of 10 or fewer primary particles are referred to as pseudo-single particles.

[0030] In the present invention, "D min "D 50 " and "D max " is the particle size value of the volume cumulative distribution of the positive electrode active material measured using the laser diffraction method. Specifically, D min This is the smallest particle diameter shown in the volume cumulative distribution, and D 50 This is the particle size when the cumulative volume is 50%, and D max This is the maximum particle size shown in the volume cumulative distribution. The particle size value of the volume cumulative distribution can be measured, for example, by dispersing the positive electrode active material in a dispersion medium, introducing it into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), irradiating it with ultrasound at approximately 28 kHz with an output of 60 W, and then obtaining a volume cumulative particle size distribution graph.

[0031] The inventors of this invention have diligently conducted research to develop a large battery that achieves high capacity and excellent safety. As a result, they have discovered that by using a positive electrode active material consisting of a single primary particle and / or a pseudo-single particle, which is an aggregate of 10 or fewer primary particles, the safety of the large battery is significantly improved, and have completed the present invention.

[0032] Specifically, the lithium secondary battery according to the present invention includes an electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction, a battery case in which the electrode assembly is housed, and a seal that seals the open end of the battery case.

[0033] The configuration of the lithium secondary battery of the present invention will be described in detail below.

[0034] electrode assembly The electrode assembly has a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive and negative electrode plates are wound in one direction, and can be, for example, a jelly roll type electrode assembly.

[0035] Figure 1 shows the laminated structure of the electrode assembly according to the present invention before winding, and Figure 2 shows the cross-sectional structure of the electrode plate (positive electrode plate or negative electrode plate) according to the present invention.

[0036] Referring to Figures 1 and 2, the electrode assembly of the present invention can be manufactured by winding a laminate formed by stacking a separator 12, a positive electrode plate 10, another separator 12, and a negative electrode plate 11 in order at least once, in one direction X.

[0037] Here, the positive electrode plate 10 and the negative electrode plate 11 have a structure in which an active material layer 21 is formed on a sheet-like current collector 20, and the current collector 20 may include a blank portion 22 in which the active material layer 21 is not formed in a part of the current collector 20.

[0038] As described above, by using a positive electrode plate 10 and a negative electrode plate 11 that include a blank portion 22, it is possible to realize a battery with a tabless structure in which at least a portion of the blank portion of the positive electrode plate 10 and the negative electrode plate 11 defines an electrode tab, without the need for a separate electrode tab.

[0039] Specifically, the blank portion 22 can be formed along the winding direction X at the end of one side of the current collector 20, and a current collector plate can be attached to the blank portion of the positive electrode plate and the blank portion of the negative electrode plate, and the current collector plate can be connected to the electrode terminals to realize a tabless battery structure.

[0040] For example, a tabless battery can be manufactured by the following method. First, a separator, a positive electrode plate, a separator, and a negative electrode plate are stacked in order so that the blank portions 22 of the positive electrode plate 10 and the negative electrode plate 11 are positioned in opposite directions, and then the assembly is wound in one direction to manufacture an electrode assembly. After that, the blank portions 22 of the positive electrode plate and the negative electrode plate are bent in the direction of the winding center C, and then current collector plates are welded to the blank portions of the positive electrode plate and the negative electrode plate, respectively, and the current collector plates are connected to the electrode terminals to manufacture a tabless battery. On the other hand, the current collector plate has a larger cross-sectional area than strip-type electrode tabs, and since resistance is inversely proportional to the cross-sectional area of ​​the current-flowing path, the cell resistance can be greatly reduced when a secondary battery is formed with the above structure.

[0041] On the other hand, the blank portions of the positive and negative electrode plates may be processed into a plurality of independently bendable segmented pieces, and at least a portion of the plurality of segmented pieces may be bent toward the winding center C of the electrode assembly.

[0042] The segmented pieces can be formed by processing the current collectors of the positive and negative electrode plates using metal foil cutting processes such as laser notching, ultrasonic cutting, and punching.

[0043] When the plain areas of the positive and negative electrode plates are processed into multiple segmented pieces, the stress applied to the plain areas during bending can be reduced, preventing deformation and damage to the plain areas, and improving the welding characteristics with the current collector plate.

[0044] The current collector plate and the blank section are generally joined by welding, and to improve welding properties, strong pressure must be applied to the weld area of ​​the blank section to bend it as flat as possible. However, during such bending, the shape of the blank section may become irregularly distorted and deformed, and the deformed area may come into contact with the electrode of the opposite polarity, causing an internal short circuit, or it may cause microscopic cracks in the blank section. However, if the blank sections of the positive and negative electrode plates are processed into multiple segmented pieces that can be bent independently, the stress applied to the blank section during bending can be reduced, minimizing deformation and damage to the blank section.

[0045] Furthermore, if the plain portion is processed into segmented pieces as described above, overlapping occurs between multiple segmented pieces when bent, which increases the welding strength with the current collector plate. When using advanced technologies such as laser welding, it is possible to prevent the laser from penetrating into the electrode assembly and melting the separator or active material. Preferably, at least a portion of the bent segmented pieces may overlap on the upper and lower ends of the electrode assembly, and the current collector plate can be bonded to the overlapping segmented pieces.

[0046] On the other hand, the electrode assembly according to the present invention can be formed in a structure in which an insulating layer 24 is further formed on the positive electrode plate 10, as shown in Figure 5. Specifically, the insulating layer 24 can be formed along a direction parallel to the winding direction of the electrode assembly so as to cover a part of the positive electrode active material layer and a part of the plain area.

[0047] In the case of a battery with a tabless structure that uses the blank portion 22c of the positive electrode plate 10 and the blank portion 22a of the negative electrode plate 11 as electrode tabs, the electrode assembly is formed such that the positive electrode plate 10 protrudes above the separator 12 and the negative electrode plate 11 protrudes below the separator 12. The protruding positive electrode plate 10 and / or negative electrode plate 11 are then bent and connected to the current collector plate. However, when the positive electrode plate 10 or negative electrode plate 11 is bent as described above, the current collector of the positive electrode plate 10 or negative electrode plate 11 extends beyond the separator and comes into close proximity to the electrode of the opposite polarity. This can cause the positive electrode plate and negative electrode plate to make electrical contact, potentially leading to an internal short circuit. However, as shown in Figure 5, when an insulating layer 24 is formed that covers the positive electrode active material layer and a portion of the blank portion, the insulating layer 24 can prevent the positive electrode plate 10 and negative electrode plate 11 from making electrical contact, thereby preventing a short circuit from occurring inside the battery.

[0048] Preferably, the insulating layer 24 can be provided on at least one surface of the positive electrode plate 10 current collector, and preferably on both sides of the positive electrode plate 10.

[0049] Furthermore, the insulating layer 24 can be formed in the region of the positive electrode plate 10 that may face the active material layer 21a of the negative electrode plate 11. For example, in the plain portion 22c of the positive electrode plate 10, the insulating layer 24 can be formed extending to the end of the plain portion 22c on the side that faces the negative electrode plate 11 after being bent. However, in the case of the opposite side of the side that faces the negative electrode plate 11 after being bent, it is preferable that the insulating layer 24 be formed only up to a part of the plain portion 22c, for example, just before the bending point of the plain portion 22c. This is because if the insulating layer 24 is formed over the entire plain portion on the opposite side of the side that faces the negative electrode plate 11, electrical contact with the current collector plate becomes impossible, and it cannot function as an electrode tab.

[0050] On the other hand, the insulating layer 24 only needs to be able to adhere to the positive electrode plate while ensuring insulating performance, and its material and components are not particularly limited. For example, the insulating layer may be an insulating coating layer or an insulating tape, and the insulating coating layer may contain an organic binder and inorganic particles. Here, the organic binder may be, for example, styrene-butadiene rubber (SBR), and the inorganic particles may be alumina oxide, but are not limited to these.

[0051] Next, each component of the electrode assembly of the present invention will be described in more detail.

[0052] (1) Positive plate The positive electrode plate may, for example, consist of a structure in which a positive electrode active material layer is formed on one or both sides of a long sheet-like positive electrode current collector, and the positive electrode active material layer may contain positive electrode active material and, selectively, a conductive material and / or a binder.

[0053] Specifically, the positive electrode plate can be manufactured by applying a positive electrode slurry, which is prepared by dispersing a positive electrode active material, a conductive material, and / or a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, to one or both sides of a long sheet-like positive electrode current collector, removing the solvent from the positive electrode slurry in a drying process, and then rolling it. On the other hand, a positive electrode plate can be manufactured that includes a blank area by not applying the positive electrode slurry to a part of the positive electrode current collector, for example, one end of the positive electrode current collector.

[0054] Various positive electrode current collectors used in the art can be used as the positive electrode current collector. For example, the positive electrode current collector can be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. The positive electrode current collector can usually have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to increase the adhesion strength of the positive electrode active material. The positive electrode current collector can be used in various forms, such as film, sheet, foil, mesh, porous material, foam, nonwoven fabric, etc.

[0055] In the present invention, the positive electrode plate contains a positive electrode active material consisting of a single particle made up of one primary particle and / or a pseudo-single particle which is an aggregate of 10 or fewer primary particles.

[0056] Traditionally, spherical secondary particles, composed of tens to hundreds of primary particles aggregated together, have been commonly used as the positive electrode active material for lithium secondary batteries. However, with positive electrode active materials in this form of aggregated primary particles, there is a problem that particle cracking occurs during the rolling process in the manufacturing of the positive electrode, causing primary particles to detach, and that cracks occur inside the particles during the charging and discharging process. When particle cracking or internal cracking occurs in the positive electrode active material, the contact area with the electrolyte increases, leading to increased gas generation due to side reactions with the electrolyte. Increased gas generation inside the battery increases the internal pressure, which can cause the battery to explode. In particular, when increasing the volume of a cylindrical battery, the amount of active material inside the battery increases due to the increase in volume, and this significantly increases the amount of gas generated, making the risk of battery ignition and / or explosion even greater.

[0057] In contrast, positive electrode active materials in the form of single particles or pseudo-single particles, where 10 or fewer primary particles are aggregated, have higher particle strength compared to existing positive electrode active materials in the form of secondary particles, where tens to hundreds of primary particles are aggregated. As a result, particle cracking during rolling is almost completely eliminated. Furthermore, in the case of single-particle or pseudo-single-particle positive electrode active materials, the small number of primary particles that make up the particle reduces the volume expansion and contraction of the primary particles during charging and discharging, which significantly reduces the occurrence of cracks inside the particle.

[0058] Therefore, when using a positive electrode active material consisting of single particles and / or pseudo-single particles, as in the present invention, the amount of gas generated due to particle cracking and internal cracking can be significantly reduced, thereby achieving excellent safety even in large batteries.

[0059] On the other hand, the single particles and / or pseudo-single particles are preferably included in an amount of 95% to 100% by weight, preferably 98% to 100% by weight, more preferably 99% to 100% by weight, and even more preferably 100% by weight, based on the total weight of the positive electrode active material contained in the positive electrode plate. When the content of single particles and / or pseudo-single particles satisfies the above range, sufficient safety can be obtained when applied to large batteries. This is because if the positive electrode active material in the form of secondary particles is included in an amount exceeding 5% by weight of the total positive electrode active material, the derivative generated from the secondary particles during electrode manufacturing and charging / discharging increases side reactions with the electrolyte, reducing the gas generation suppression effect, which may reduce the stability improvement effect when applied to large batteries.

[0060] On the other hand, the positive electrode active material containing single particles and / or pseudo-single particles according to the present invention is D min The diameter can be 1.0 μm or larger, 1.1 μm or larger, 1.15 μm or larger, 1.2 μm or larger, 1.25 μm or larger, 1.3 μm or larger, or 1.5 μm or larger. minIf the particle size is less than 1.0 μm, the voltage increases during the rolling process of the positive electrode plate, making it prone to particle cracking and reducing thermal stability. This makes it difficult to ensure sufficient thermal stability when applied to large cylindrical batteries.

[0061] On the other hand, considering the resistance and output characteristics, the D of the positive electrode active material min This can be 3 μm or less, 2.5 μm or less, or 2 μm or less. min If the value is too large, the lithium ion diffusion distance within the particle increases, which can degrade resistance and power characteristics.

[0062] For example, the D of the positive electrode active material min The particle size can be 1.0 μm to 3 μm, 1.0 μm to 2.5 μm, or 1.3 μm to 2.0 μm.

[0063] On the other hand, the positive electrode active material is D 50 The particle size can be 5 μm or less, 4 μm or less, or 3 μm or less, for example, 0.5 μm to 5 μm, preferably 1 μm to 5 μm, and more preferably 2 μm to 5 μm. Single-particle and / or pseudo-single-particle positive electrode active materials have a problem of lower lithium mobility than secondary-particle positive electrode active materials because there are fewer interfaces between primary particles that serve as diffusion pathways for lithium ions within the particles, which increases resistance. This increase in resistance becomes more severe as the particle size increases, and increased resistance adversely affects capacitance and power characteristics. Therefore, the D of the positive electrode active material 50 By adjusting the particle size to 5 μm or less, the lithium ion diffusion distance within the positive electrode active material particles can be minimized, thereby suppressing the increase in resistance.

[0064] Furthermore, the positive electrode active material is D max The diameter can be 12 μm to 17 μm, preferably 12 μm to 16 μm, and more preferably 12 μm to 15 μm. D of the positive electrode active material max When the above range is satisfied, better resistance and capacitance characteristics are exhibited. D of the positive electrode active material maxIf the ratio is too large, aggregation occurs between single particles, and the lithium migration pathway within the aggregated particles becomes longer, reducing lithium mobility and potentially increasing resistance. On the other hand, the D of the positive electrode active material max If the size is too small, an excessive crushing process will be performed, and due to the excessive crushing, D min The particle size can become smaller than 1 μm, which can cause particle cracking during rolling and reduce thermal stability.

[0065] On the other hand, the positive electrode active material may have a particle size distribution (PSD) represented by the following formula (1) of 3 or less, preferably 2 to 3, and more preferably 2.3 to 3.

[0066] Equation (1): Particle size distribution (PSD) = (D max -D min ) / D 50

[0067] When the positive electrode active material has the particle size distribution described above, the electrode density of the positive electrode can be appropriately maintained, and particle cracking and increased resistance can be effectively suppressed.

[0068] On the other hand, the positive electrode active material can have an average particle size of primary particles of 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, and more preferably 2 μm to 5 μm. When the average particle size of the primary particles satisfies the above range, a positive electrode active material in the form of single particles and / or pseudo-single particles with excellent electrochemical properties can be formed. If the average particle size of the primary particles is too small, the number of aggregated primary particles forming the positive electrode active material increases, reducing the effect of suppressing particle cracking during rolling. If the average particle size of the primary particles is too large, the lithium diffusion path inside the primary particles becomes longer, increasing resistance and potentially degrading the output characteristics.

[0069] In the present invention, it is preferable that the positive electrode active material has a unimodal particle size distribution. Conventionally, in order to improve the electrode density of the positive electrode active material layer, bimodal positive electrode active materials have been widely used, which are a mixture of large-particle positive electrode active material with a large average particle size and small-particle positive electrode active material with a small average particle size. However, in the case of positive electrode active materials in single-particle or pseudo-single-particle form, as the particle size increases, the lithium migration path becomes longer and the resistance increases significantly. Therefore, when large-particle particles are mixed and used, problems may arise in which the capacity and output characteristics deteriorate. Accordingly, in the present invention, the increase in resistance can be minimized by using a positive electrode active material having a unimodal distribution.

[0070] On the other hand, the positive electrode active material may include a lithium nickel-based oxide, specifically a lithium nickel-based oxide containing 80 mol% or more of Ni relative to the total number of moles of the transition metal. Preferably, the lithium nickel-based oxide may contain Ni in amounts of 80 mol% or more but less than 100 mol%, 82 mol% or more but less than 100 mol%, or 83 mol% or more but less than 100 mol%. As described above, when a lithium nickel-based oxide with a high Ni content is used, a high capacity can be achieved.

[0071] More specifically, the positive electrode active material may include a lithium nickel-based oxide represented by the following [Chemical Formula 1].

[0072] [Chemical formula 1] Li a Ni b Co c M 1 d M 2 e O2

[0073] In the above chemical formula 1, M 1 This can be Mn, Al, or a combination thereof, preferably Mn or Mn and Al.

[0074] Said M 2is one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, preferably can be one or more selected from the group consisting of Zr, Y, Mg, and Ti, and more preferably can be Zr, Y, or a combination thereof. M 2 The element is not necessarily included, but when included in an appropriate amount, it can play a role in promoting grain growth during firing or improving crystal structure stability.

[0075] The above-mentioned a represents the lithium molar ratio in the lithium nickel-based oxide, and can be 0.8 ≤ a ≤ 1.2, 0.85 ≤ a ≤ 1.15, or 0.9 ≤ a ≤ 1.2. When the molar ratio of lithium satisfies the above range, the crystal structure of the lithium nickel-based oxide can be stably formed.

[0076] The above-mentioned b represents the molar ratio of nickel among all the metals other than lithium in the lithium nickel-based oxide, and can be 0.8 ≤ b < 1, 0.82 ≤ b < 1, 0.83 ≤ b < 1, 0.85 ≤ b < 1, 0.88 ≤ b < 1, or 0.90 ≤ b < 1. When the molar ratio of nickel satisfies the above range, it shows a high energy density and enables the realization of a high capacity.

[0077] The above-mentioned c represents the cobalt molar ratio among all the metals other than lithium in the lithium nickel-based oxide, and can be 0 < c < 0.2, 0 < c < 0.18, 0.01 ≤ c ≤ 0.17, 0.01 ≤ c ≤ 0.15, 0.01 ≤ c ≤ 0.12, or 0.01 ≤ c ≤ 0.10. When the molar ratio of cobalt satisfies the above range, good resistance characteristics and output characteristics can be realized.

[0078] The above-mentioned d represents the molar ratio of the M 1 element among all the metals other than lithium in the lithium nickel-based oxide, and can be 0 < d < 0.2, 0 < d < 0.18, 0.01 ≤ d ≤ 0.17, 0.01 ≤ d ≤ 0.15, 0.01 ≤ d ≤ 0.12, or 0.01 ≤ d ≤ 0.10. When the molar ratio of the M 1 element satisfies the above range, the structure stability of the positive electrode active material is excellent.

[0079] The aforementioned e is M of the total metals other than lithium in the lithium nickel oxide. 2 This indicates the molar ratio of elements and can be either 0 ≤ e ≤ 0.1 or 0 ≤ e ≤ 0.05.

[0080] On the other hand, the positive electrode active material according to the present invention may further include, if necessary, a coating layer on the surface of the lithium nickel oxide particles, which contains one or more coating elements selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S. Preferably, the coating element may be Al, B, Co, or a combination thereof.

[0081] When a coating layer is present on the surface of lithium nickel oxide particles, the coating layer suppresses contact between the electrolyte and the lithium composite transition metal oxide, thereby reducing the leaching of transition metals and the generation of gases due to side reactions with the electrolyte.

[0082] The positive electrode active material may be present in an amount of 80 to 99% by weight, preferably 85 to 99% by weight, and more preferably 90 to 99% by weight, relative to the total weight of the positive electrode active material layer.

[0083] Next, the conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it does not cause chemical changes in the battery and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Of these, one or more can be used. The conductive material can usually be included in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0084] The binder plays a role in improving adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, based on the total weight of the positive electrode active material layer.

[0085] On one hand, an insulating layer covering a part of the positive electrode active material layer and a part of the non-coated area can be further formed on the positive electrode plate according to the need. The insulating layer can be formed along a direction parallel to the winding direction of the electrode assembly.

[0086] (2) Negative electrode plate The negative electrode plate can have a structure in which a negative electrode active material layer is formed on one or both sides of a long sheet-like negative electrode current collector, and the negative electrode active material layer can contain a negative electrode active material, a conductive material, and a binder.

[0087] Specifically, the negative electrode plate can be manufactured by applying a negative electrode slurry produced by dispersing a negative electrode active material, a conductive material, and a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc. on one or both sides of a sheet-like negative electrode current collector, removing the solvent of the negative electrode slurry by a drying process, and then rolling. On the other hand, when applying the negative electrode slurry, a negative electrode plate including a non-coated area can be manufactured by a method of not applying the negative electrode slurry to a partial area of the negative electrode current collector, for example, one end of the negative electrode current collector.

[0088] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium can be used. Specific examples of the negative electrode active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; silicon-based materials such as Si, Si-Me alloy (where Me is one or more selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, and Ni), SiOy (where 0 < y < 2), and Si-C composite; lithium metal thin film; metal materials capable of alloying with lithium such as Sn and Al; etc. Any one or a mixture of two or more of these can be used.

[0089] Preferably, the negative electrode plate according to the present invention can contain a silicon-based negative electrode active material. The silicon-based negative electrode active material can be Si, Si-Me alloy (where Me is one or more selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, and Ni), SiOy (where 0 < y < 2), Si-C composite, or a combination thereof, and preferably can be SiOy (where 0 < y < 2). Since the silicon-based negative electrode active material has a high theoretical capacity, when the silicon-based negative electrode active material is included, the capacity characteristics can be improved.

[0090] On the other hand, the silicon-based negative electrode active material can be doped with M b metal, where the M b metal can be a Group 1 metal element or a Group 2 metal element, and specifically can be Li, Mg, etc. Specifically, the silicon negative electrode active material can be Si, SiOy (where 0 < y < 2), Si-C composite, etc. doped with M b metal. In the case of a metal-doped silicon-based negative electrode active material, although the capacity of the active material decreases somewhat due to the doping element, since it has high efficiency, a high energy density can be realized.

[0091] Further, the silicon-based negative electrode active material can further include a carbon coating layer on the surface of the particles. Here, the carbon coating amount can be 20% by weight or less, preferably 1 - 20% by weight, based on the total weight of the silicon-based negative electrode active material.

[0092] Also, the negative electrode plate can further include a carbon-based negative electrode active material as a negative electrode active material as needed. The carbon-based negative electrode active material can be, for example, artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, etc., but is not limited thereto.

[0093] On the other hand, when a mixture of silicon-based and carbon-based anode active materials is used as the anode active material, the mixing ratio of the silicon-based and carbon-based anode active materials can be 1:99 to 20:80 by weight, preferably 1:99 to 15:85, and more preferably 1:99 to 10:90.

[0094] The negative electrode active material may be present in an amount of 80 to 99% by weight, preferably 85 to 99% by weight, and more preferably 90 to 99% by weight, relative to the total weight of the negative electrode active material layer.

[0095] On the other hand, as the negative electrode current collector, a negative electrode current collector commonly used in the art can be used, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy can be used. The negative electrode current collector can usually have a thickness of 3 to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, nonwoven fabric.

[0096] The conductive material is used to impart conductivity to the negative electrode and can be used without particular limitations in the battery it is configured in, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Of these, one or more can be used. The conductive material can usually be included in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the negative electrode active material layer.

[0097] The binder plays a role in improving adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more can be used. The binder may be present in an amount of 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight, relative to the total weight of the negative electrode active material layer.

[0098] (3) Separator The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. It can be used without particular limitations as long as it is a separator commonly used in lithium secondary batteries. Specifically, the separator can be a porous polymer film, such as a porous polymer film made from polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. Alternatively, a conventional porous nonwoven fabric, such as a nonwoven fabric made from high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength.

[0099] Lithium-ion rechargeable battery Next, the lithium secondary battery according to the present invention will be described.

[0100] The lithium secondary battery according to the present invention may include an electrode assembly having a structure in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction, a battery case in which the electrode assembly is housed, and a seal that seals the open end of the battery case.

[0101] Preferably, the lithium secondary battery according to the present invention may be a cylindrical battery, and more preferably, it may be a large cylindrical battery having a form factor ratio (defined as the ratio of diameter (Φ) to height (H) of the cylindrical battery, i.e., the ratio of diameter (Φ) to height (H)) of 0.4 or more. Here, form factor refers to the values ​​indicating the diameter and height of the cylindrical battery.

[0102] The cylindrical battery according to the present invention can be, for example, a 46110 cell (diameter 46 mm, height 110 mm, form factor ratio 0.418), a 4875 cell (diameter 48 mm, height 75 mm, form factor ratio 0.640), a 48110 cell (diameter 48 mm, height 110 mm, form factor ratio 0.436), a 4880 cell (diameter 48 mm, height 80 mm, form factor ratio 0.600), or a 4680 cell (diameter 46 mm, height 80 mm, form factor ratio 0.575). In the numerical value indicating the form factor, the first two digits indicate the diameter of the cell, and the next two or three digits indicate the height of the cell.

[0103] The lithium secondary battery according to the present invention applies a positive electrode active material in the form of a single particle and / or pseudo-single particle to significantly reduce gas generation compared to conventional batteries, thereby achieving excellent safety even in large cylindrical batteries with a form factor ratio of 0.4 or higher.

[0104] On the other hand, the lithium secondary battery according to the present invention may preferably be a tabless battery that does not include electrode tabs, but is not limited thereto.

[0105] The aforementioned tablet-like battery may have a structure in which, for example, the positive electrode plate and the negative electrode plate each include a blank portion on which no active material layer is formed, the blank portions of the positive electrode plate and the negative electrode plate are located at the upper and lower ends of the electrode assembly, a current collector plate is bonded to the blank portions of the positive electrode plate and the negative electrode plate, and the current collector plate is connected to the electrode terminals.

[0106] Figure 3 shows a cross-sectional view of a tablet-type battery according to one embodiment of the present invention. The lithium secondary battery according to one embodiment of the present invention will be described below with reference to Figure 3. However, Figure 3 is merely an illustration of one embodiment of the present invention, and the structure of the lithium secondary battery of the present invention is not limited to the scope disclosed in Figure 3.

[0107] A lithium secondary battery 140 according to one embodiment of the present invention includes a jelly roll type electrode assembly 141, a battery can 142 in which the electrode assembly 141 is housed, and a seal 143 that seals the open end of the battery can 142.

[0108] Here, the positive electrode plate and the negative electrode plate of the electrode assembly may each include a blank portion where no active material layer is formed, and the electrode assembly can be laminated and wound up such that the blank portion of the positive electrode and the blank portion of the negative electrode are located at the upper and lower ends, respectively. Since the electrode assembly has been described above, only the remaining components other than the electrode assembly will be described below.

[0109] The battery casing 142 is a container with an opening formed at the top and is made of a conductive metal material such as aluminum or steel. The battery casing houses the electrode assembly 141 in its inner space through the upper opening, and also houses the electrolyte.

[0110] The electrolyte used in this invention can be any type of electrolyte suitable for lithium secondary batteries, such as organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, or molten inorganic electrolytes, and the type is not particularly limited.

[0111] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0112] The organic solvent can be used without particular limitations as long as it serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group, which can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0113] The lithium salt can be used without particular limitations as long as it is a compound that can provide lithium ions for use in lithium secondary batteries. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably used within the range of 0.1 to 5.0 M, more preferably 0.1 to 3.0 M. When the concentration of the lithium salt falls within this range, the electrolyte can exhibit excellent electrolyte performance due to having appropriate conductivity and viscosity, and lithium ions can move effectively.

[0114] In addition to the electrolyte components, the electrolyte may further contain additives for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. For example, the additives may be, but are not limited to, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethyl phosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, either alone or in combination. The additives may be present in an amount of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, relative to the total weight of the electrolyte.

[0115] The battery can 142 is electrically connected to the blank portion 146b of the negative electrode plate and functions as a negative electrode terminal that contacts an external power source and transmits the current applied from the external power source to the negative electrode plate.

[0116] If necessary, a beading portion 147 and a crimping portion 148 may be provided at the upper end of the battery can 142. The beading portion 147 can be formed by press-fitting the periphery of the outer surface of the battery can 142 to a distance D1. The beading portion 147 can function as a support on which the seal 143 is placed, preventing the electrode assembly 141 housed inside the battery can 142 from detaching through the upper end opening of the battery can 142.

[0117] The crimping portion 148 can be formed on the upper part of the beading portion 147 and has an extended and folded shape that encloses the outer circumferential surface and a portion of the upper surface of the cap plate 143a which is placed on the beading portion 147.

[0118] Next, the sealing body 143 is for sealing the open end of the battery can 142 and includes a cap plate 143a, a first gasket 143b that provides airtightness and insulation between the cap plate 143a and the battery can 142, and may further include a connecting plate 143c electrically and mechanically coupled to the cap plate 143a as needed. The cap plate 143a can be crimped onto a beading portion 147 formed on the battery can 142 and secured by a crimping portion 148.

[0119] The cap plate 143a is a component made of a conductive metal material and covers the upper opening of the battery can 142. The cap plate 143a is electrically connected to the positive electrode plate of the electrode assembly 141 and electrically insulated from the battery can 142 via the first gasket 143b. Therefore, the cap plate 143a can function as the positive electrode terminal of the secondary battery. The cap plate 143a may have a projection 143d formed to project upward from its center C, and the projection 143d may come into contact with an external power source so that current can be applied from the external power source.

[0120] A first gasket 143b can be interposed between the cap plate 143a and the crimping portion 148 to ensure airtightness of the battery can 142 and to provide electrical insulation between the battery can 142 and the cap plate 143a.

[0121] On the other hand, the lithium secondary battery 140 according to the present invention may further include current collector plates 144 and 145 as needed. The current collector plates are coupled to the blank portion 146a of the positive electrode plate and the blank portion 146b of the negative electrode plate and are connected to the electrode terminals (i.e., the positive electrode terminal and the negative electrode terminal).

[0122] Specifically, the lithium secondary battery 140 according to the present invention may include a first current collector plate 144 connected to the upper part of the electrode assembly 141 and a second current collector plate 145 connected to the lower part of the electrode assembly 141.

[0123] The system may further include a first current collector plate 144 and / or a second current collector plate 145.

[0124] The first current collector plate 144 is coupled to the upper part of the electrode assembly 141. The first current collector plate 144 is made of a conductive metal material such as aluminum, copper, or nickel, and is electrically connected to the blank portion 146a of the positive electrode plate. A lead 149 can be coupled to the first current collector plate 144. The lead 149 can extend above the electrode assembly 141 and be coupled to the coupling plate 143c, or it can be directly coupled to the lower surface of the cap plate 143a. The lead 149 can be coupled to other components by welding. Preferably, the first current collector plate 144 can be formed integrally with the lead 149. In this case, the lead 149 can have an elongated plate shape extending outward from the center of the first current collector plate 144.

[0125] On the other hand, the first current collector plate 144 is coupled to the end of the blank portion 146a of the positive electrode plate, and this coupling can be performed by methods such as laser welding, resistance welding, ultrasonic welding, or soldering.

[0126] The second current collector plate 145 is coupled to the lower part of the electrode assembly 141. The second current collector plate 145 is made of a conductive metal material such as aluminum, copper, or nickel, and is electrically connected to the blank portion 146b of the negative electrode plate. One side of the second current collector plate 145 can be coupled to the blank portion 146b of the negative electrode plate, and the opposite side can be coupled to the inner bottom surface of the battery can 142. Here, the coupling can be performed by methods such as laser welding, resistance welding, ultrasonic welding, or soldering.

[0127] On the other hand, the battery 140 according to the present invention may further include an insulating member (insulator) 146 as needed. The insulating member 146 may be positioned to cover the upper surface of the first current collector plate 144. By covering the first current collector plate 144 with the insulating member 146, it is possible to prevent the first current collector plate 144 from coming into direct contact with the inner surface of the battery can 142.

[0128] The insulating member 146 is provided with a lead hole 151 through which a lead 149 extending upward from the first current collector plate 144 is drawn out. The lead 149 is drawn out upward through the lead hole 151 and coupled to the lower surface of the connecting plate 143c or the lower surface of the cap plate 143a.

[0129] The insulating member 146 can be made of an insulating polymer resin, such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

[0130] On the other hand, the battery 140 according to the present invention may further include a venting portion 152 formed on the lower surface of the battery can 142, if necessary. The venting portion 152 corresponds to a region on the lower surface of the battery can 142 that has a thinner thickness than the surrounding region. Because the venting portion 152 is thin, it is structurally more brittle than the surrounding region. Therefore, if the pressure inside the battery 140 increases above a certain level, the venting portion 152 will rupture, releasing the gas inside the battery can 142 to the outside, thus preventing the battery from exploding.

[0131] Figure 4 shows a cross-sectional view of a tablet-type battery according to another embodiment of the present invention. The battery according to another embodiment of the present invention will be described below with reference to Figure 4. However, Figure 4 shows one embodiment of the present invention, and the structure of the battery of the present invention is not limited to the scope disclosed in Figure 4.

[0132] Referring to Figure 4, the battery 170 according to another embodiment of the present invention differs from the battery 140 shown in Figure 3 in the structure of the battery case and seal, while the electrode assembly and electrolyte configuration are substantially identical.

[0133] Specifically, the battery 170 according to another embodiment includes a battery can 171 through which a rivet terminal 172 is installed. The rivet terminal 172 is installed on a partially closed closed surface (upper surface in the drawing) at one end of the battery can 171. The rivet terminal 172 is riveted into the through hole (first opening at the first end) of the battery can 171 with an insulating second gasket 173 interposed between them. The rivet terminal 172 is exposed to the outside in the direction opposite to the direction of gravity.

[0134] The rivet terminal 172 includes a terminal exposure portion 172a and a terminal insertion portion 172b. The terminal exposure portion 172a is exposed to the outside of the closed surface of the battery can 171. The terminal exposure portion 172a can be located approximately in the center of the partially closed surface of the battery can 171. The maximum diameter of the terminal exposure portion 172a can be made larger than the maximum diameter of the through hole formed in the battery can 171. The terminal insertion portion 172b can penetrate approximately in the center of the partially closed surface of the battery can 171 and be electrically connected to the blank portion 146a of the positive electrode plate. The terminal insertion portion 172b can be rivet-bonded to the inner surface of the battery can 171. That is, the end of the terminal insertion portion 172b can have a shape that curves toward the inner surface of the battery can 171. The maximum diameter of the end of the terminal insertion portion 172b can be larger than the maximum diameter of the through hole in the battery can 171.

[0135] The lower end surface of the terminal insertion portion 172b can be welded to the first current collector plate 144, which is connected to the blank portion 146a of the positive electrode plate. An insulating cap 174 made of an insulating material can be interposed between the first current collector plate 144 and the inner surface of the battery can 171. The insulating cap 174 covers the upper part of the first current collector plate 144 and the upper edge portion of the electrode assembly 141. This prevents the blank portion on the outer circumference of the electrode assembly 141 from coming into contact with the inner surface of the battery can 171, which has a different polarity, and causing a short circuit. The terminal insertion portion 172b of the rivet terminal 172 can be welded to the first current collector plate 144 by passing through the insulating cap 174.

[0136] The second gasket 173 is interposed between the battery can 171 and the rivet terminal 172 to prevent electrical contact between the battery can 171 and the rivet terminal 172, which have opposite polarities. This allows the upper surface of the rivet terminal 172, which has a substantially flat shape, to function as the positive terminal of the battery 170.

[0137] The second gasket 173 includes a gasket exposed portion 173a and a gasket inserted portion 173b. The gasket exposed portion 173a is interposed between the terminal exposed portion 172a of the rivet terminal 172 and the battery can 171. The gasket inserted portion 173b is interposed between the terminal inserted portion 172b of the rivet terminal 172 and the battery can 171. The gasket inserted portion 173b deforms together with the terminal inserted portion 172b during reveting, and can adhere tightly to the inner surface of the battery can 171. The second gasket 173 can be made of, for example, an insulating polymer resin.

[0138] The gasket exposed portion 173a of the second gasket 173 may have a shape that extends to cover the outer circumferential surface of the terminal exposed portion 172a of the rivet terminal 172. When the second gasket 173 covers the outer circumferential surface of the rivet terminal 172, it is possible to prevent short circuits from occurring during the process of connecting electrical connecting components such as busbars to the upper surface of the battery can 171 and / or the rivet terminal 172. Although not shown in the drawings, the gasket exposed portion 173a may have a shape that extends to cover not only the outer circumferential surface of the terminal exposed portion 172a but also a part of the upper surface.

[0139] When the second gasket 173 is made of a polymer resin, the second gasket 173 can be bonded to the battery can 171 and the rivet terminal 172 by heat fusion. In this case, the airtightness at the bonding interface between the second gasket 173 and the rivet terminal 172 and the bonding interface between the second gasket 173 and the battery can 171 can be enhanced. On the other hand, when the gasket exposed portion 173a of the second gasket 173 extends to the upper surface of the terminal exposed portion 172a, the rivet terminal 172 can be integrally bonded to the second gasket 173 by insert injection.

[0140] The remaining area 175 on the upper surface of the battery can 171, excluding the area occupied by the rivet terminal 172 and the second gasket 173, corresponds to the negative terminal having the opposite polarity to the rivet terminal 172.

[0141] The second current collector plate 176 is connected to the lower part of the electrode assembly 141. The second current collector plate 176 is made of a conductive metal material such as aluminum, steel, copper, or nickel, and is electrically connected to the blank portion 146b of the negative electrode plate.

[0142] Preferably, the second current collector plate 176 is electrically connected to the battery can 171. For this purpose, the second current collector plate 176 can be fixed by interposing at least a portion of its edge between the inner surface of the battery can 171 and the first gasket 178b. In one example, at least a portion of the edge of the second current collector plate 176 can be fixed to the beading portion 180 formed at the lower end of the battery can 171 by welding, while being supported by the lower end surface of the beading portion 180. In a modified example, at least a portion of the edge of the second current collector plate 176 can be directly welded to the inner wall surface of the battery can 171.

[0143] The second current collector plate 176 may have a plurality of radially arranged bumps (not shown) on the surface facing the plain portion 146b. If bumps are formed, the second current collector plate 176 can be pressed to press the bumps into the plain portion 146b.

[0144] Preferably, the end of the second current collector plate 176 and the blank portion 146b can be joined by welding, for example, laser welding.

[0145] The sealing body 178 that seals the lower open end of the battery can 171 includes a cap plate 178a and a first gasket 178b. The first gasket 178b electrically isolates the cap plate 178a from the battery can 171. The crimping portion 181 secures both the edge of the cap plate 178a and the first gasket 178b. The cap plate 178a is provided with a vent portion 179. The configuration of the vent portion 179 is substantially the same as that of the embodiment described above.

[0146] Preferably, the cap plate 178a is made of a conductive metal material. However, since the first gasket 178b is interposed between the cap plate 178a and the battery can 171, the cap plate 178a does not have electrical polarity. The seal 178 seals the open end at the bottom of the battery can 171 and functions to release gas when the internal pressure of the battery cell 170 increases above a critical value.

[0147] Preferably, the rivet terminal 172 electrically connected to the blank portion 146a of the positive electrode plate is used as the positive electrode terminal. Also, the portion 175 of the upper surface of the battery can 171, which is electrically connected to the blank portion 146b of the negative electrode plate via the second current collector plate 176, other than the rivet terminal 172, is used as the negative electrode terminal. In this way, when the two electrode terminals are located on the top of the battery, electrical connecting components such as busbars can be placed on only one side of the battery 170. This simplifies the battery pack structure and improves energy density. Furthermore, since the portion 175 used as the negative electrode terminal has a substantially flat shape, a sufficient contact area can be secured when joining electrical connecting components such as busbars. As a result, the battery 170 can reduce the resistance at the joint of the electrical connecting components to a desirable level.

[0148] When a lithium secondary battery is formed in a tabless structure as described above, current concentration is reduced compared to conventional batteries with electrode tabs. This effectively reduces heat generation inside the battery, thereby improving the thermal stability of the battery.

[0149] The lithium secondary battery of the present invention, as described above, can be used in the manufacture of a battery pack. Figure 6 schematically illustrates the configuration of a battery pack according to an embodiment of the present invention. Referring to Figure 6, the battery pack 3 according to an embodiment of the present invention includes an assembly of electrically connected secondary batteries 1 and a pack housing 2 that houses them. Here, the secondary battery 1 is a battery cell according to the embodiment described above. For the convenience of illustration, the drawings omit the depiction of components such as busbars for the electrical connection of the secondary batteries 1, cooling units, and external terminals.

[0150] Battery pack 3 can be installed in a vehicle. The vehicle may, for example, be an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle may include four-wheeled vehicles or two-wheeled vehicles.

[0151] Figure 7 is a diagram illustrating the automobile including the battery pack 3 shown in Figure 6.

[0152] Referring to Figure 7, an automobile 5 according to one embodiment of the present invention includes a battery pack 3 according to one embodiment of the present invention and operates by receiving power from the battery pack 3.

[0153] The present invention will be described in more detail below with reference to specific examples.

[0154] [Example 1] It has a unimodal particle size distribution, D min =1.78μm, D 50 =4.23μm, D max =13.1μm, and the positive electrode active material (composition: Li[Ni 0.9 Co 0.06 Mn 0.03 Al 0.01 [O2] was prepared. Figure 8 shows an SEM image of the positive electrode active material used in Example 1.

[0155] A positive electrode slurry was prepared by mixing a positive electrode active material, carbon nanotubes, and a PVDF binder in a weight ratio of 97.8:0.6:1.6 in N-methylpyrrolidone. The positive electrode slurry was applied to one surface of an aluminum current collector sheet, dried at 120°C, and then rolled to produce a positive electrode plate.

[0156] A negative electrode slurry was prepared by mixing a negative electrode active material (graphite:SiO=95:5 weight ratio mixture), a conductive material (Super C), styrene-butadiene rubber (SBR), and carboxymethylcellulose (CMC) in water in a weight ratio of 96:2:1.5:0.5. After applying the negative electrode slurry to one surface of a copper current collector sheet, it was dried at 150°C and then rolled to produce a negative electrode plate.

[0157] A separator was placed between the positive and negative electrode plates manufactured as described above, and the plates were stacked in the order of separator / positive electrode plate / separator / negative electrode plate. After stacking, the assembly was wound up to produce a jelly roll type electrode assembly. After inserting the electrode assembly manufactured as described above into a battery case, electrolyte was injected to produce a 4680 cell.

[0158] [Example 2] As the positive electrode active material, it has a unimodal particle size distribution, D min =1.38μm, D 50 =4.69μm, D max =18.5μm, and the positive electrode active material (composition: Li[Ni 0.9 Co 0.06 Mn 0.03 Al 0.01 4680 cells were manufactured in the same manner as in Example 1, except that ]O2) was used. Figure 9 shows an SEM image of the cathode active material used in Example 2.

[0159] [Comparative Example 1] As the positive electrode active material, large particle size average particle size D 50 The small particle size is 9 μm, and the average particle size D 50 The positive electrode active material (composition: Li[Ni) has a bimodal particle size distribution of 4 μm and is in the form of secondary particles. 0.9 Co 0.05 Mn 0.04 Al 0.01 4680 cells were manufactured in the same manner as in Example 1, except that ]O2) was used.

[0160] [Comparative Example 2] As the positive electrode active material, it has a unimodal particle size distribution, D min = 0.892 μm, D 50 =3.02μm, D max =11μm, and the positive electrode active material (composition: Li[Ni 0.9 Co 0.06 Mn 0.03 Al 0.01 4680 cells were manufactured in the same manner as in Example 1, except that ]O2) was used.

[0161] Figure 10 shows an SEM image of the positive electrode active material used in Comparative Example 2.

[0162] [Experimental Example 1] A hot box test was performed on the 4680 cells produced according to Examples 1-2 and Comparative Examples 1-2.

[0163] Specifically, each of the 4680 cells produced in Example 1 and Comparative Example 1 was placed in a hot box chamber at room temperature, heated to 130°C at a heating rate of 5°C / min, maintained at that temperature for 30 minutes, and then the temperature change of the battery was measured. A "Pass" was indicated if no thermal runaway or ignition occurred during the test, and a "Fail" was indicated if thermal runaway and / or ignition occurred. Furthermore, for accuracy, the cells from Examples 1 and 2 were tested at least twice.

[0164] The measurement results are shown in Table 1 and Figures 11 and 12 below. Figure 11 is a graph showing the hotbox test results for 4680 cells produced by Sample 1 of Example 1 and Comparative Example 1, and Figure 12 is a graph showing the hotbox test results for 4680 cells produced by Samples 2 and 3 of Example 1, Samples 1 and 2 of Example 2 and Comparative Example 2.

[0165] [Table 1]

[0166] Referring to Table 1, Figure 11, and Figure 12, D min In the case of the cylindrical battery of Example 1, which uses a positive electrode active material in the form of a single particle / pseudo-single particle with a diameter of 1.0 μm or more, the battery voltage and temperature are stably maintained until 65 minutes have elapsed, whereas in Comparative Examples 1 and D, which use secondary particles as the positive electrode active material... minIn Comparative Example 2, a lithium secondary battery using a positive electrode active material in single-particle / pseudo-single-particle form with a particle size of less than 1.0 μm showed a rapid increase in battery temperature.

[0167] [Experimental Example 2] After rolling the positive electrode plates manufactured in Example 1 and Comparative Example 1, the plates were cut using an ion milling apparatus to check the degree of cracking of the positive electrode active material particles, and the cross-sections were then photographed with a scanning electron microscope (SEM). Figure 13 shows a cross-sectional SEM image of the positive electrode plate manufactured in Example 1, and Figure 14 shows a cross-sectional SEM image of the positive electrode plate manufactured in Comparative Example 1.

[0168] Referring to Figures 13 and 14, the positive electrode plate of Example 1 showed almost no cracking of the positive electrode active material particles after rolling, whereas the positive electrode plate of Comparative Example 2, which used secondary particles, showed numerous cracks in the positive electrode active material particles after rolling. [Explanation of symbols]

[0169] 10 Positive plate 11 Negative plate 12 Separators 20 Current collector 21, 21a Active material layer 22, 22a, 22c, 146b Plain part 24 Insulating layer 140, 170 cylindrical batteries 141 Electrode assembly 142, 171 Battery cans 143, 178 Sealed body 144 First current collection plate 145, 176 Second current collection plate 146 Insulating material (insulator) 152 Venting section 172 Rivet terminals 173 Second Gasket 147 Beading section 148 Crimping section 149 Reed

Claims

1. A secondary battery comprising an electrode assembly in which a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate are wound in one direction, a battery case in which the electrode assembly is housed, and a seal that seals the open end of the battery case, The positive electrode plate comprises a positive electrode active material including single particles, pseudo-single particles, or a combination thereof. The positive electrode active material has a particle size distribution (PSD) of 3 or less, represented by the following formula (1), and a D min of 1.0 μm or more. The positive electrode active material comprises a lithium nickel-based oxide containing 80 mol% or more of Ni relative to the total number of moles of transition metals, in a lithium secondary battery. Equation (1): Particle size distribution (PSD) = (D ｍａｘ -D ｍｉｎ ) / D ５０

2. The positive electrode active material is D ５０ The lithium secondary battery according to claim 1, wherein the diameter is 5 μm or less.

3. The positive electrode active material is D ｍａｘ The lithium secondary battery according to claim 1, wherein the diameter is 12 μm to 17 μm.

4. The positive electrode active material is D ｍｉｎ The lithium secondary battery according to claim 1, wherein the particle size is 1.3 μm or larger.

5. The lithium secondary battery according to claim 1, wherein the positive electrode active material has a unimodal particle size distribution showing a single peak in a volume cumulative particle size distribution graph.

6. The lithium secondary battery according to claim 1, wherein the single particle, pseudo-single particle, or combination thereof is included in an amount of 95% to 100% by weight relative to the total weight of the positive electrode active material contained in the positive electrode plate.

7. The lithium secondary battery according to claim 1, wherein the positive electrode active material includes a lithium nickel-based oxide represented by the following [Chemical Formula 1]. [Chemical formula 1] Li ａ Ni ｂ Co ｃ M １ ｄ M ２ ｅ O ２ In the above chemical formula 1, M １ M is Mn, Al, or a combination thereof. ２ is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and satisfies the following conditions: 0.8 ≤ a ≤ 1.2, 0.83 ≤ b < 1, 0 < c < 0.17, 0 < d < 0.17, and 0 ≤ e ≤ 0.

1.

8. The lithium secondary battery according to claim 1, wherein the positive electrode active material has an average particle size of primary particles of 0.5 μm to 5 μm.

9. The lithium secondary battery according to claim 1, wherein the negative electrode plate includes a silicon-based negative electrode active material.

10. The lithium secondary battery according to claim 1, wherein the negative electrode plate comprises a silicon-based negative electrode active material and a carbon-based negative electrode active material.

11. The lithium secondary battery according to claim 10, wherein the silicon-based anode active material and the carbon-based anode active material are contained in a weight ratio of 1:99 to 20:

80.

12. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a cylindrical battery having a form factor ratio of 0.4 or more, and the form factor is the value obtained by dividing the diameter of the cylindrical battery by its height.

13. The lithium secondary battery according to claim 12, wherein the lithium secondary battery is a 46110-cell, 4875-cell, 48110-cell, 4880-cell, or 4680-cell battery.

14. The positive electrode plate and the negative electrode plate each include a blank area where no active material layer is formed. The lithium secondary battery according to claim 1, wherein at least a portion of the blank portion of the positive electrode plate or the negative electrode plate defines an electrode tab.

15. The blank portion of the positive electrode plate and the blank portion of the negative electrode plate are each formed at the end of one side of the positive electrode plate and the negative electrode plate, along the direction in which the electrode assembly is wound. A current collector plate is attached to the blank portion of the positive electrode plate and the blank portion of the negative electrode plate, The lithium secondary battery according to claim 14, wherein the current collection plate is connected to the electrode terminals.

16. The blank portion of the positive electrode plate and the blank portion of the negative electrode plate are processed into a plurality of segmented pieces that can be independently folded. The lithium secondary battery according to claim 15, wherein at least a portion of the plurality of segmented pieces is bent toward the winding center of the electrode assembly.

17. At least some of the bent segments overlap on the upper and lower ends of the electrode assembly. The lithium secondary battery according to claim 16, wherein the current collection plate is bonded to the overlapping plurality of segmented pieces.

18. The 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, covering a portion of the positive electrode active material layer and a portion of the blank portion.

19. The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer. The lithium secondary battery according to claim 1, wherein the positive electrode active material is contained in an amount of 90% to 99% by weight relative to the total weight of the positive electrode active material layer.

20. A battery pack comprising a lithium secondary battery according to any one of claims 1 to 19.

21. An automobile comprising the battery pack described in claim 20.

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