Cylindrical battery, battery pack including the same, and motor vehicle

Abstract

A cylindrical battery according to an embodiment of the present invention includes an electrode assembly having a first uncoated portion and a second uncoated portion defined as an electrode tab, a battery housing that receives the electrode assembly through an opening and is electrically connected to the second uncoated portion, an electrode terminal that is riveted through a through hole formed in a closing portion of the battery housing and is electrically connected to the first uncoated portion, an insulating gasket interposed between the electrode terminal and the through hole, and a cap plate configured to cover the opening of the battery housing. The electrode terminal includes a body portion inserted into the through hole, an outer flange portion extending from a periphery of one side of the body portion exposed to an outer surface of the closing portion along an outer surface of the closing portion, an inner flange portion extending from a periphery of the other side of the body portion exposed to an inner surface of the closing portion toward an inner surface of the closing portion, and a flat portion provided on the inside of the inner flange portion.

Description

Technical Field

[0001] The present invention relates to a cylindrical battery, a battery pack including the same, and a vehicle. More specifically, the present invention relates to a cylindrical battery having a structure in which a positive electrode terminal and a negative electrode terminal are both disposed adjacent to one side of the cylindrical battery without significantly deforming the structure of a conventional cylindrical battery, a battery pack including the same, and a vehicle.

[0002] This application claims priority based on Korean Patent Application No. 10-2021-0142178 filed on October 22, 2021, and all of the contents disclosed in the specification and drawings of the application are incorporated herein by reference.

Background Art

[0003] Generally, when manufacturing a battery pack using cylindrical batteries, a plurality of cylindrical batteries are erected and arranged in a housing, and the upper and lower ends of the cylindrical batteries are respectively utilized as a positive electrode terminal and a negative electrode terminal to electrically connect the plurality of cylindrical batteries to each other.

[0004] In the electrical connection of a cylindrical battery, the non-coated portion of the negative electrode of the electrode assembly housed inside the battery housing extends downward and is electrically connected to the bottom surface of the battery housing, and the non-coated portion of the positive electrode extends upward and is electrically connected to the top cap. That is, in a cylindrical battery, it is common that the bottom surface of the battery housing is used as a negative electrode terminal, and the top cap covering the upper end opening of the battery housing is used as a positive electrode terminal.

[0005] When the positive electrode terminal and the negative electrode terminal of the cylindrical battery are located on opposite sides, electrical connection components such as bus bars for electrically connecting the plurality of cylindrical batteries must be applied to both the upper and lower portions of the cylindrical battery. This complicates the electrical connection structure of the battery pack.

[0006] Furthermore, in such a structure, components for insulation and components for ensuring waterproofness and airtightness are respectively applied to the upper and lower parts of the battery pack, resulting in an increase in the number of applied components and a complication of the structure.

[0007] Therefore, in order to simplify the electrical connection structure of a plurality of cylindrical batteries, there is a demand for the development of a cylindrical battery having a structure in which the positive and negative terminals are applied in the same direction.

[0008] On the other hand, secondary batteries with high applicability for each product group, capable of repeating charge and discharge, and having electrical characteristics such as high energy density are widely applied not only to portable devices but also to electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by an electric drive source. Hereinafter, the battery refers to a secondary battery.

[0009] Batteries are attracting attention as a new energy source for improving energy efficiency because they not only have the primary advantage of significantly reducing the use of fossil fuels but also are environmentally friendly in that they do not generate any by-products from the use of energy.

[0010] Currently, batteries such as lithium-ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel metal hydride batteries, and nickel zinc batteries are widely used, and the operating voltage of a single battery is about 2.5V to 4.5V. Therefore, when a higher output voltage is required, a plurality of batteries are connected in series to form a battery pack. Also, depending on the charge and discharge capacity required for the battery pack, a plurality of batteries may be connected in parallel to form a battery pack. Therefore, the number of batteries included in the battery pack and the electrical connection form can be variously set according to the required output voltage and / or charge and discharge capacity.

[0011] On one hand, as types of unit batteries, cylindrical, prismatic, and pouch-type batteries are known. In the case of a cylindrical battery, a separator, which is an insulator, is interposed between the positive electrode and the negative electrode, and this is wound up to form a jelly-roll type electrode assembly, which is inserted inside a battery housing to constitute a battery. And strip-shaped electrode tabs are connected to the plain portions of the positive electrode and the negative electrode respectively, and the electrode tabs electrically connect between the electrode assembly and the electrode terminals exposed to the outside. For reference, the positive electrode terminal is the cap plate of the sealing body that seals the opening of the battery housing, and the negative electrode terminal is the battery housing.

[0012] However, according to the conventional cylindrical battery having such a structure, since the current is concentrated on the strip-shaped electrode tabs coupled to the positive electrode plain portion and / or the negative electrode plain portion, there is a problem that the resistance is large, heat generation is much, and the current collection efficiency is not good.

[0013] In the case of a small cylindrical battery having a form factor of 1865 or 2170, the problems of large resistance and heat generation do not occur. However, when increasing the form factor for applying the cylindrical battery to an electric vehicle, there is a risk that the cylindrical battery catches fire while a large amount of heat is generated around the electrode tabs during the rapid charging process.

[0014] In order to solve such problems, a cylindrical battery (so-called tab-less cylindrical battery) having a structure in which the positive electrode plain portion and the negative electrode plain portion are respectively located at the upper end and the lower end of the jelly-roll type electrode assembly, and a current collector plate is welded to such a plain portion to improve the current collection efficiency has been proposed.

[0015] Figs. 1 to 3 are diagrams showing the manufacturing process of the tab-less cylindrical battery. Fig. 1 shows the structure of the electrode, Fig. 2 shows the winding process of the electrode, and Fig. 3 shows the process in which the current collector plate is welded to the folded surface of the plain portion. Fig. 4 is a cross-sectional view of the tab-less cylindrical battery cut along the longitudinal direction (Y-axis direction).

[0016] Referring to FIGS. 1 to 4, the positive electrode 10 and the negative electrode 11 have a structure in which an active material layer 21 is coated on a sheet-shaped current collector 20, and include a plain portion 22 on one long side along the winding direction X.

[0017] The electrode assembly A is manufactured by sequentially laminating the positive electrode 10 and the negative electrode 11 together with two separator membranes 12 as shown in FIG. 2, and then winding them in one direction (X-axis direction). At this time, the plain portion of the positive electrode 10 and the plain portion of the negative electrode 11 are arranged in opposite directions.

[0018] After the winding process, the plain portion 10a of the positive electrode 10 and the plain portion 11a of the negative electrode 11 are bent toward the core side. Then, current collector plates 30 and 31 are welded and joined to the plain portions 10a and 11a, respectively.

[0019] No separate electrode tabs are connected to the positive electrode plain portion 10a and the negative electrode plain portion 11a, and the current collector plates 30 and 31 are connected to external electrode terminals, and the current path is formed with a large cross-sectional area along the winding axis direction (refer to the arrow) of the electrode assembly A, so there is an advantage that the resistance of the battery can be reduced. This is because the resistance is inversely proportional to the cross-sectional area of the path through which the current flows.

[0020] However, when the form factor of the cylindrical battery increases and the charging current during rapid charging becomes large, the problem of heat generation occurs again even in the tabless cylindrical battery.

[0021] Specifically, as shown in FIG. 4, the conventional tabless cylindrical battery 40 includes a battery housing 41 and a sealing body 42. The sealing body 42 includes a cap plate 42a, a sealing gasket 42b, and a connecting plate 42c. The sealing gasket 42b wraps around the periphery of the cap plate 42a and is fixed by a crimping portion 43. Also, the electrode assembly A is fixed in the battery housing 41 by a beading portion 44 to prevent vertical movement.

[0022] Generally, the positive terminal is the cap plate 42a of the sealing body 42, and the negative terminal is the battery housing 41. Therefore, the current collector plate 30 coupled to the plain portion 10a of the positive electrode 10 is electrically connected to the connection plate 42c attached to the cap plate 42a through the strip-shaped lead 45. Also, the current collector plate 31 coupled to the plain portion 11a of the negative electrode 11 is electrically connected to the bottom of the battery housing 41. The insulator 46 covers the current collector plate 30 to prevent the battery housing 41 with a different polarity from coming into contact with the plain portion 10a of the positive electrode 10 and causing a short circuit.

[0023] When the current collector plate 30 is connected to the connection plate 42c, the strip-shaped lead 45 is used. The lead 45 is separately attached to the current collector plate 30 or integrally manufactured with the current collector plate 30. However, since the lead 45 is in a thin strip shape, its cross-sectional area is small, and a large amount of heat is generated when a rapid charging current flows. Also, the excessive heat generated in the lead 45 is transmitted to the electrode assembly A side and causes the separator 12 to contract, which may cause an internal short circuit, which is a main cause of thermal runaway.

[0024] Also, the lead 45 occupies a considerable installation space within the battery housing 41. Therefore, the cylindrical battery 40 including the lead 45 has low space efficiency and is limited in increasing the energy density.

[0025] Furthermore, in order to connect the conventional tabless cylindrical batteries 40 in series and / or in parallel, bus bar components must be connected to the cap plate 42a of the sealing body 42 and the bottom surface of the battery housing 41, resulting in a decrease in space efficiency. The battery pack mounted on an electric vehicle includes hundreds of cylindrical batteries 40. Therefore, the inefficiency of electrical wiring also causes considerable inconvenience during the assembly process of the electric vehicle and during the maintenance of the battery pack.

[0026] On the one hand, when manufacturing an electrode by applying a conventional positive electrode active material containing secondary particles, particle cracking occurs, and gas generation increases due to internal cracks generated during charge and discharge, which may cause problems in battery stability.

[0027] In an attempt to solve this problem, a positive electrode active material in the form of single particles or pseudo-single particles with a relatively large primary particle size has been developed. However, when applying the single particle or pseudo-single particle form of positive electrode active material to a high-loading electrode and rolling it, the electrode cracks before the porosity of the electrode reaches the target level, and there are problems that the resistance characteristics and charge-discharge efficiency of the lithium secondary battery are not good.

Summary of the Invention

Problems to be Solved by the Invention

[0028] The present invention has been made in view of the above-described problems, and an object thereof is to provide a cylindrical battery having a structure in which a positive electrode terminal and a negative electrode terminal are applied in the same direction.

[0029] Further, when attempting to electrically connect a plurality of cylindrical batteries in one direction, another object of the present invention is to ensure a sufficient area for welding an electrical connection component such as a bus bar for manufacturing a battery pack and an electrode terminal of the cylindrical battery.

[0030] Further, another object of the present invention is to increase the energy density by reducing the internal resistance of the cylindrical battery by improving the structure of the electrode terminal of the cylindrical battery to increase the space efficiency inside the battery housing.

[0031] Further, another object of the present invention is to improve the problem of internal heat generation occurring during rapid charging by improving the structure of the electrode terminal of the cylindrical battery to expand the cross-sectional area of the current path.

[0032] Furthermore, another object of the present invention is to provide a cylindrical battery with an improved structure that allows electrical wiring work for series and / or parallel connection of cylindrical batteries to be performed only on one side of the cylindrical battery.

[0033] Furthermore, another object of the present invention is to provide a battery pack manufactured using a cylindrical battery having an improved structure, and an automobile including the same.

[0034] Furthermore, another object of the present invention is to provide an electrode and an electrode assembly including the same, which have excellent thermal stability by applying single particles or pseudo single particles as a positive electrode active material, high electrical conductivity, and high rolling characteristics.

[0035] Furthermore, another object of the present invention is to provide an electrode assembly with improved energy density by including a silicon-based negative electrode active material in the negative electrode.

[0036] Furthermore, another object of the present invention is to provide an electrode assembly with an increased section of the positive electrode active material portion without concern for lithium precipitation.

[0037] Furthermore, another object of the present invention is to provide a cylindrical battery that can exhibit excellent thermal stability even when the volume of the battery increases due to an increase in the form factor.

[0038] The technical problems to be solved by the present invention are not limited to the above problems, and other problems will be clearly understood by those of ordinary skill in the art from the following description of the invention.

Means for Solving the Problems

[0039] To achieve the above problems, a cylindrical battery according to an aspect of the present invention includes an electrode assembly in which a first electrode, a second electrode, and a separator interposed therebetween are wound around a winding axis to define a core and an outer peripheral surface.

[0040] The first electrode and the second electrode each include a first non-coated portion and a second non-coated portion along the winding direction where the active material layer is not coated, and the first non-coated portion and the second non-coated portion can be defined as electrode tabs themselves.

[0041] The cylindrical battery includes a battery housing that houses the electrode assembly through an opening formed on one side and is electrically connected to the second non-coated portion, and a riveting through a through hole formed in a closing portion provided on the side opposite to the opening of the battery housing, and an electrode terminal electrically connected to the first non-coated portion, an insulating gasket interposed between the electrode terminal and the through hole, and a cap plate configured to cover the opening of the battery housing.

[0042] The electrode terminal may include a main body portion inserted into the through hole, an external flange portion extending along the outer surface of the closing portion from one side peripheral edge of the main body portion exposed on the outer surface of the closing portion of the battery housing, an internal flange portion extending toward the inner surface of the closing portion from the other side peripheral edge of the main body portion exposed on the inner surface of the closing portion, and a flat portion provided inside the internal flange portion.

[0043] The cap plate is insulated from the battery housing and has no polarity because it is not electrically connected to the electrode assembly.

[0044] The surface of the electrode terminal exposed outside the battery housing is the first electrode terminal, and a portion of the outer surface of the closing portion of the battery housing parallel to the upper surface of the first electrode terminal may be the second electrode terminal.

[0045] The flat portion and the inner surface of the closing portion may be parallel to each other.

[0046] The angle between the internal flange portion and the inner surface of the closing portion may be between 0° and 60°.

[0047] It may be provided with a structure of an asymmetric groove between the inner flange portion and the flat portion. Indentation A portion may be provided.

[0048] The asymmetric groove may include a side wall of the flat portion and an inclined surface of the inner flange portion connected to an end of the side wall.

[0049] The side wall may be perpendicular to the inner surface of the closing portion.

[0050] The thickness of the inner flange portion may decrease as it gets farther from the main body portion.

[0051] The insulating gasket includes an external gasket interposed between the external flange portion and the outer surface of the closing portion, and an internal gasket interposed between the inner flange portion and the inner surface of the closing portion, and the thickness of the internal gasket and the external gasket may be different depending on the position.

[0052] The thickness of the region interposed between the inner edge of the through hole connected to the inner surface of the closing portion and the inner flange portion in the region of the internal gasket may be relatively thinner than other regions.

[0053] The inner edge of the through hole may include a facing surface facing the inner flange portion.

[0054] The internal gasket may extend longer than the inner flange portion.

[0055] Based on the inner surface of the closing portion, the height of the flat portion may be higher than or the same as the height of the end of the internal gasket.

[0056] Based on the inner surface of the closing portion, the height of the flat portion may be higher than or the same as the height of the end of the inner flange portion.

[0057] The radius from the center of the main body portion to the periphery of the external flange portion may be 10% to 60% based on the radius of the closing portion.

[0058] The radius from the center of the main body part to the periphery of the flat part can be 4% to 30% based on the radius of the closed part.

[0059] The first non-patterned part may include a plurality of independently bendable segmented pieces. The plurality of segmented pieces of the first non-patterned part can form a bending surface of the segmented piece at one end of the electrode assembly while being bent toward the core side. In this case, the electrode terminal can be electrically connected to the bending surface of the segmented piece of the first non-patterned part.

[0060] The cylindrical battery may further include a first current collector plate coupled to the bending surface of the segmented piece of the first non-patterned part, and an insulator interposed between the first current collector plate and the inner surface of the closed part. In this case, the flat part of the electrode terminal can pass through the insulator and be coupled to the first current collector plate.

[0061] The second non-patterned part may include a plurality of independently bendable segmented pieces. The plurality of segmented pieces of the second non-patterned part can form a bending surface of the segmented piece at the other end of the electrode assembly while being bent toward the core side. In this case, the battery housing can be electrically connected to the bending surface of the segmented piece of the second non-patterned part.

[0062] The cylindrical battery may further include a second current collector plate coupled to the bending surface of the segmented piece of the second non-patterned part. In this case, at least a part of the periphery of the second current collector plate can extend toward the inner surface of the beading part and be interposed and fixed between the inner surface of the beading part and the sealing gasket.

[0063] The boundary region between the patterned part and the non-patterned part of the first electrode includes a first slide part where the thickness of the active material layer decreases, and the boundary region between the patterned part and the non-patterned part of the second electrode includes a second slide part where the thickness of the active material layer decreases. The first slide part and the second slide part can be located in opposite directions in the winding axis direction.

[0064] The grounded portion of the first electrode includes a loading reduction portion where the loading amount of the active material decreases, and the position of the loading reduction portion may correspond to the position of the second sliding portion.

[0065] The active material layer of the first electrode may include a positive electrode active material containing single particles, pseudo single particles, or a combination thereof.

[0066] The minimum particle size D appearing in the volume cumulative distribution of the positive electrode active material min may be 1.0 μm or more.

[0067] In the volume cumulative distribution of the positive electrode active material, the particle size D when the volume cumulative amount is 50% 50 may be 5.0 μm or less.

[0068] The maximum particle size D appearing in the volume cumulative distribution of the positive electrode active material max may be 12 μm to 17 μm.

[0069] The positive electrode active material has a unimodal particle size distribution in which a single peak appears in the volume cumulative particle size distribution graph, and the particle size distribution (PSD: Particle Size Distribution) represented by the following formula 1 may be 3 or less. [Formula 1] Particle size distribution (PSD) = (D max - D min ) / D 50

[0070] The single particles, pseudo single particles, or a combination thereof may be contained in an amount of 95 wt% to 100 wt% based on the total weight of the positive electrode active material contained in the active material layer of the first electrode.

[0071] The positive electrode active material may include a lithium nickel-based oxide containing 80 mol% or more of Ni based on the total number of moles of transition metals.

[0072] The active material layer of the first electrode may have a porosity of 15% to 23%.

[0073] The active material layer of the first electrode may contain flaky graphite in a weight ratio of 0.05 wt% to 5 wt%.

[0074] The active material layer of the first electrode may further contain carbon nanotubes (CNTs).

[0075] The active material layer of the second electrode may contain a silicon-based negative electrode active material and a carbon-based negative electrode active material.

[0076] The silicon-based negative electrode active material and the carbon-based negative electrode active material may be included in the active material layer of the second electrode at a weight ratio of 1:99 to 20:80.

[0077] A battery pack according to another aspect of the present invention includes a plurality of cylindrical batteries having at least one of the above-described features, and a pack housing for accommodating the same.

[0078] An automobile according to still another aspect of the present invention includes the above-described battery pack.

Advantages of the Invention

[0079] According to one aspect of the present invention, a cylindrical battery having a structure in which a positive electrode terminal and a negative electrode terminal are applied in the same direction is provided, so that the electrical connection structure of a plurality of cylindrical batteries can be simplified.

[0080] Also, according to one aspect of the present invention, since the electrode terminal of the cylindrical battery has a sufficient area to be welded to an electrical connection component such as a bus bar, the bonding strength between the electrode terminal and the electrical connection component can be sufficiently ensured, and the resistance at the bonding site between the electrical connection component and the electrode terminal can be reduced to a desirable level.

[0081] Also, according to one aspect of the present invention, by improving the structure of the electrode terminal of the cylindrical battery to increase the space efficiency in the battery housing, the internal resistance of the cylindrical battery can be reduced and the energy density can be increased.

[0082] Moreover, according to one aspect of the present invention, by improving the structure of the electrode terminal of the cylindrical battery to increase the cross-sectional area of the current path, the problem of internal heat generation during rapid charging can be improved.

[0083] Moreover, according to one aspect of the present invention, the electrical wiring work for the series and / or parallel connection of the cylindrical batteries can be performed on one side of the cylindrical battery.

[0084] Moreover, according to one aspect of the present invention, a battery pack manufactured using a cylindrical battery having an improved structure, and an automobile including the same can be provided.

[0085] Moreover, according to one aspect of the present invention, by applying single-particle-based active material particles as the positive electrode active material and minimizing gas generation due to particle cracking during electrode manufacturing and internal cracks during charge and discharge, excellent safety can be realized even in a large-sized cylindrical battery with an increased volume.

[0086] Moreover, according to one aspect of the present invention, D min By including a positive electrode active material powder having a particle size of 1.0 μm or more in the positive electrode, the thermal stability of the battery can be further improved. According to the research of the present inventors, even when single particles and / or pseudo single particles are applied as the positive electrode active material, it has been confirmed that the effect of suppressing particle cracking after rolling and improving thermal stability varies depending on the particle size of the positive electrode active material powder. In particular, when particles having a particle size of less than 1.0 μm are included in the positive electrode active material powder, the linear pressure increases during the rolling process, resulting in an increase in particle cracking and a decrease in thermal stability, and sufficient thermal stability could not be ensured when applied to a large-sized cylindrical battery. Therefore, in the present invention, by using a positive electrode active material powder in which the minimum particle size D min is controlled to be 1.0 μm or more, the effect of improving thermal stability can be maximized.

[0087] Moreover, according to one aspect of the present invention, D 50 D maxBy including a positive electrode active material powder with an appropriately adjusted particle size distribution (PSD) in the positive electrode, an increase in resistance due to the application of single particles can be minimized, and thus excellent capacity characteristics and output characteristics can be realized.

[0088] Also, according to one aspect of the present invention, the conductivity of the electrode can be improved by including a single-particle type positive electrode active material coated with a conductive coating layer or by including a novel CNT as a conductive material.

[0089] Also, according to one aspect of the present invention, since the positive electrode active material layer contains flaky graphite, when the positive electrode active material layer is rolled, the flaky graphite provides a sliding effect to the positive electrode active material, improving the rolling characteristics of the electrode and reducing the electrode porosity to a target level. As a result, the stability, initial resistance characteristics, and charge / discharge efficiency of the cylindrical battery are improved.

[0090] Also, according to one aspect of the present invention, a higher energy density can be realized by including a silicon-based negative electrode active material with a large capacity in the negative electrode.

[0091] Also, according to one aspect of the present invention, since the positive electrode includes a loading reduction portion with a small loading amount of the positive electrode active material, the section of the positive electrode active material portion can be increased without worry about lithium precipitation.

[0092] Also, according to one aspect of the present invention, compared with a conventional battery having a strip-shaped electrode tab, the internal heat generation of the battery can be effectively reduced, and thus the thermal stability of the battery can be improved.

[0093] The present invention also has various other effects, which will be described later with reference to embodiments. However, descriptions of effects that can be easily inferred by ordinary technicians will be omitted.

[0094] The following drawings attached to this specification illustrate desirable embodiments of the present invention and serve to further understand the technical idea of the present invention together with the detailed description of the invention. Therefore, the present invention should not be construed as being limited only to the matters described in the drawings.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0096] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and the claims are not to be construed as limited to ordinary and dictionary meanings. The inventors themselves shall interpret them in accordance with the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that they can appropriately define the concept of the terms in order to explain the invention in the best way. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, there may be various equivalents and modifications that can replace them at the time of this application.

[0097] Also, for the purpose of assisting in the understanding of the invention, the attached drawings are not illustrated to actual scale, and the dimensions of some components may be exaggerated. Also, the same reference numerals may be assigned to the same components in different embodiments.

[0098] The sizes and thicknesses of the illustrated components are arbitrarily shown for convenience of explanation, and the present invention is not necessarily limited by the illustration. In the drawings, in order to clearly show many layers and regions, the thickness is enlarged. Also, in the drawings, for convenience of explanation, the thicknesses of some layers and regions are exaggerated.

[0099] Also, when a part such as a layer, film, region, or plate is said to be "on" or "above" another part, this includes not only the case where it is "directly above" the other part, but also the case where there are other parts in between. Conversely, when a part is said to be "directly above" another part, it means that there are no other parts in between. Also, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" in the opposite direction to gravity.

[0100] Throughout the specification, unless otherwise specifically mentioned, when a part "includes" other components, it means that it may further include other components rather than excluding them.

[0101] Throughout the specification, when a "plan view" is mentioned, it means the case of looking at the target part from above, and when a "cross-sectional view" is mentioned, it means the case of looking at the cross-section obtained by vertically cutting the target part from the side.

[0102] Referring to FIGS. 5 to 7, a cylindrical battery 1 according to an embodiment of the present invention includes an electrode assembly A, a battery housing BH, a cap plate 60, and an electrode terminal 50.

[0103] In addition to the above-described components, the cylindrical battery 1 may further include an insulating gasket 35 and / or a first current collector plate 36 and / or an insulator 37 and / or a second current collector plate 38 and / or a sealing gasket 39.

[0104] The electrode assembly A includes a first electrode having a first polarity, a second electrode having a second polarity, and a separator interposed between the first electrode and the second electrode. The first electrode is a positive electrode or a negative electrode, and the second electrode corresponds to an electrode having a polarity opposite to that of the first electrode.

[0105] The electrode assembly A may have, for example, a jelly roll structure. That is, the electrode assembly A can be manufactured by winding a laminate formed by sequentially laminating the first electrode, the separator, and the second electrode at least once around a winding center C. In this case, a separator may be further provided on the outer peripheral surface of the electrode assembly A for insulation from the battery housing BH.

[0106] The first electrode includes a first current collector and a first electrode active material coated on one or both surfaces of the first current collector. At one end of the first current collector in the width direction (Z-axis direction), there is a non-coated portion (first non-coated portion) of the first electrode where the first electrode active material is not coated. The first non-coated portion functions as a first electrode tab 13. The first electrode tab 13 is provided at the upper part in the height direction (Z-axis direction) of the electrode assembly A housed in the battery housing BH.

[0107] The second electrode includes a second current collector and a second electrode active material coated on one or both surfaces of the second current collector. At the other end of the second current collector in the width direction (Z-axis direction), there is a non-coated portion (second non-coated portion) of the second electrode where the second electrode active material is not coated. The second non-coated portion functions as a second electrode tab 14. The second electrode tab 14 is provided at the lower part in the height direction (Z-axis direction) of the electrode assembly A housed in the battery housing BH.

[0108] The first electrode tab 13 and the second electrode tab 14 extend and protrude in opposite directions along the width direction of the electrode assembly A, that is, the height direction (Z-axis direction) of the cylindrical battery 1.

[0109] Referring to FIGS. 5 to 8, the battery housing BH is a substantially cylindrical container with an opening formed downward, and is made of a material having conductivity such as metal. The material of the battery housing BH can be, for example, aluminum or steel. The side surface (outer peripheral surface) and the upper surface of the battery housing BH can be integrally formed. The upper surface (a plane parallel to the X-Y plane) of the battery housing BH has a substantially flat form. The upper part located on the opposite side of the opening is referred to as a closing portion. The battery housing BH houses the electrode assembly A through the opening formed downward and also houses the electrolyte together.

[0110] The battery housing BH is electrically connected to the electrode assembly A. The battery housing BH is electrically connected to, for example, the second electrode tab 14 of the electrode assembly A. In this case, the battery housing BH has the same polarity as the second electrode tab 14.

[0111] Referring to FIGS. 6 and 11, the battery housing BH may include a beading portion 23 and a crimping portion 24 formed at its lower end. The beading portion 23 is located at the lower part of the electrode assembly A. The beading portion 23 is formed by pushing in around the outer peripheral surface of the battery housing BH. The beading portion 23 can function as a support portion on which the cap plate 60 is placed so that the electrode assembly A having a size substantially corresponding to the width of the battery housing BH does not slip out from the opening formed at the lower end of the battery housing BH.

[0112] The crimping portion 24 is formed below the beading portion 23. The crimping portion 24 has a form that extends and is bent so as to wrap the outer peripheral surface of the cap plate 60 disposed below the beading portion 23 and a part of the lower surface of the cap plate 60.

[0113] However, the present invention does not exclude the case where the battery housing BH does not include such a beading portion 23 and / or crimping portion 24. In an embodiment of the present invention, when the battery housing BH does not include the beading portion 23 and / or crimping portion 24, the fixing of the electrode assembly A and / or the fixing of the cap plate 60 and / or the sealing of the battery housing BH can be achieved, for example, through the additional application of components that can function as stoppers for the electrode assembly A and / or the additional application of structures on which the cap plate 60 can be placed and / or welding between the battery housing BH and the cap plate 60.

[0114] Referring to FIGS. 6 and 11, the cap plate 60 may be made of, for example, a metal material to ensure rigidity. The cap plate 60 covers an opening formed at the lower end of the battery housing BH. That is, the cap plate 60 constitutes the lower surface of the cylindrical battery 1. In the cylindrical battery 1 according to an embodiment of the present invention, the cap plate 60 has no polarity even when it is a metal material having conductivity. Having no polarity means that the cap plate 60 is electrically insulated from the battery housing BH and the electrode terminal 50. Therefore, the cap plate 60 does not function as a positive electrode terminal or a negative electrode terminal. Therefore, the cap plate 60 does not need to be electrically connected to the electrode assembly A and the battery housing BH, and its material does not necessarily have to be a conductive metal.

[0115] When the battery housing BH according to an embodiment of the present invention includes a beading portion 23, the cap plate 60 can be placed on the beading portion 23 formed on the battery housing BH. Further, when the battery housing BH according to an embodiment of the present invention includes a crimping portion 24, the cap plate 60 is fixed by the crimping portion 24. A sealing gasket 39 may be interposed between the cap plate 60 and the crimping portion 24 of the battery housing BH to ensure the airtightness of the battery housing BH. On the other hand, as described above, the battery housing BH according to an embodiment of the present invention does not necessarily include the beading portion 23 and / or the crimping portion 24. In this case, the sealing gasket 39 may be interposed between a fixing structure provided on the opening side of the battery housing BH and the cap plate 60 to ensure the airtightness of the battery housing BH.

[0116] Referring to FIGS. 11 and 12, the cap plate 60 may further include a venting portion 41 to prevent the internal pressure from increasing beyond a preset value due to the gas generated inside the battery housing BH. The venting portion 41 corresponds to a region on the cap plate 60 that is thinner than the peripheral region. The venting portion 41 is structurally weaker than the peripheral region. Therefore, if an abnormality occurs in the cylindrical battery 1 and the internal pressure of the battery housing BH increases above a certain level, the venting portion 41 breaks and the gas generated inside the battery housing BH is discharged. The venting portion 41 can be formed, for example, by notching on one or both surfaces of the cap plate 60 to partially reduce the thickness of the cap plate 60.

[0117] The cylindrical battery 1 according to an embodiment of the present invention has a structure in which all the positive and negative terminals are present at the upper part as described later, so the structure of the upper part is more complex than that of the lower part. Therefore, a venting portion 41 may be formed on the cap plate 60 that constitutes the lower surface of the cylindrical battery 1 for smooth discharge of the gas generated inside the battery housing BH.

[0118] As shown in FIG. 11, it is desirable that the lower end portion of the cap plate 60 is located above the lower end portion of the battery housing BH. In this case, even if the lower end portion of the battery housing BH contacts the ground or the bottom surface of the housing for module or pack configuration, the cap plate 60 does not contact the ground or the bottom surface of the housing for module or pack configuration. Therefore, it is possible to prevent the phenomenon that the pressure required for breaking the venting portion 41 changes from the design value due to the weight of the cylindrical battery 1, thereby ensuring the smoothness of breaking of the venting portion 41.

[0119] On the one hand, when the bending portion 41 has a closed-loop form as shown in FIGS. 11 and 12, in terms of ease of breakage, it is more advantageous that the distance from the central portion of the cap plate 60 to the bending portion 41 is greater. This is because when the same bending pressure acts, the greater the distance from the central portion of the cap plate 60 to the bending portion 41, the greater the force acting on the bending portion 41 and the easier it is to break. Also, in terms of smooth discharge of the bending gas, it is more advantageous that the distance from the central portion of the cap plate 60 to the bending portion 41 is greater. From this perspective, it is advantageous that the bending portion 41 is formed along the periphery of a substantially flat region protruding downward (downward with reference to FIG. 11) from the peripheral region of the cap plate 60.

[0120] FIG. 12 shows a case where the bending portion 41 is continuously formed while drawing a substantially circle on the cap plate 60, but the present invention is not limited thereby. The bending portion 41 may be discontinuously formed while drawing a substantially circle on the cap plate 60, or may be formed in a substantially linear form or other forms.

[0121] Referring to FIGS. 5 to 7, the electrode terminal 50 is made of a conductive metal material and passes through the upper surface of the battery housing BH, that is, the surface located on the opposite side of the opening of the battery housing BH (a plane parallel to the X - Y plane). The electrode terminal 50 is electrically connected to, for example, the first electrode tab 13 of the electrode assembly A. In this case, the electrode terminal 50 has a first polarity. Therefore, the electrode terminal 50 can function as the first electrode terminal E1 in the cylindrical battery 1 according to an embodiment of the present invention. When the electrode terminal 50 has such a first polarity, the electrode terminal 50 is electrically insulated from the battery housing BH having a second polarity. The electrical insulation between the electrode terminal 50 and the battery housing BH can be realized in various ways. For example, insulation can be realized by interposing an insulating gasket 35 between the electrode terminal 50 and the battery housing BH. Differently, insulation may be realized by forming an insulating coating layer on a part of the electrode terminal 50. Or, a method of structurally and firmly fixing the electrode terminal 50 so that the electrode terminal 50 and the battery housing BH cannot come into contact may be applied. Or, a combination of a plurality of the above - described methods may be applied.

[0122] The electrode terminal 50 includes a terminal exposed portion 49a and a terminal insertion portion 49b. The terminal exposed portion 49a is exposed outside the battery housing BH. The terminal exposed portion 49a may be located at substantially the center of the upper surface of the battery housing BH. The maximum width of the terminal exposed portion 49a may be formed larger than the maximum width of the hole of the battery housing BH through which the electrode terminal 50 passes. The terminal insertion portion 49b may penetrate substantially the center of the upper surface of the battery housing BH and be electrically connected to the first electrode tab 13. The peripheral region of the lower end portion of the terminal insertion portion 49b may be rivet - bonded to the inner surface of the battery housing BH. That is, the peripheral region of the lower end portion of the terminal insertion portion 49b may have a form bent toward the inner surface of the battery housing BH, whereby the maximum width of the lower end portion of the terminal insertion portion 49b may be formed larger than the maximum width of the hole of the battery housing BH through which the terminal insertion portion 49b passes.

[0123] On the one hand, when the cylindrical battery 1 according to an embodiment of the present invention includes the first current collector plate 36, the central region of the lower end of the terminal insertion portion 49b can be coupled to the first current collector plate 36. The central region of the lower end of the terminal insertion portion 49b can be, for example, substantially cylindrical. The diameter of the bottom surface of the central region of the lower end of the terminal insertion portion 49b can be set to about 6.2 mm.

[0124] The connection between the bottom surface of the central region of the lower end of the terminal insertion portion 49b and the first current collector plate 36 can be performed, for example, by laser welding or ultrasonic welding.

[0125] The laser welding can be performed by irradiating a laser through a hole formed at the winding center C of the electrode assembly A to form a laser welding line on one surface of the first current collector plate 36. The laser welding line can be formed in a form that draws substantially concentric circles on the opposite surface that does not contact the bottom surface of the central region of the lower end of the terminal insertion portion 49b among the upper and lower surfaces of the first current collector plate 36. The welding line can be formed continuously or partially discontinuously.

[0126] The concentric welding line can have a diameter of about 60% to 80% of the diameter of the bottom surface of the central region of the lower end of the terminal insertion portion 49b. For example, when the diameter of the bottom surface of the central region of the lower end of the terminal insertion portion 49b is about 6.2 mm, it is desirable that the diameter of the circle drawn by the welding line is about 4.0 mm or more. If the diameter of the circle drawn by the welding line is too small, the bonding force due to welding may become insufficient. On the other hand, if the diameter of the circle drawn by the welding line is too large, the electrode assembly A may be damaged by heat and / or welding spatter, etc.

[0127] The ultrasonic welding can be performed by inserting a welding rod for ultrasonic welding through a hole formed in the winding center C of the electrode assembly A. The welded portion formed by the ultrasonic welding is formed at the contact interface between the bottom surface of the central region of the lower end portion of the terminal insertion portion 49b and the first current collector plate 36. The welded portion formed by the ultrasonic welding can be entirely formed within a concentric circle having a diameter of about 30% to 80% with respect to the bottom surface of the central region of the lower end portion of the terminal insertion portion 49b. For example, when the diameter of the bottom surface of the central region of the lower end portion of the terminal insertion portion 49b is about 6.2 mm, the diameter of the circle drawn by the welded portion by ultrasonic welding can desirably be about 2.0 mm or more. If the diameter of the circle drawn by the welded portion by ultrasonic welding is too small, the bonding force by welding may be insufficient. On the other hand, if the diameter of the circle drawn by the welded portion by ultrasonic welding is too large, the electrode assembly A may be damaged by heat and / or vibration, etc.

[0128] In one embodiment of the present invention, the upper surface of the battery housing BH and the electrode terminal 50 exposed outside the battery housing BH face the same direction while having opposite polarities. Also, a step may be formed between the electrode terminal 50 and the upper surface of the battery housing BH. Specifically, when the entire upper surface of the battery housing BH has a flat shape or has a shape protruding upward at its central portion, the terminal exposed portion 49a of the electrode terminal 50 may further protrude above the upper surface of the battery housing BH. Conversely, when the upper surface of the battery housing BH is concave at its central portion, that is, in the direction toward the electrode assembly A, the upper surface of the battery housing BH may further protrude above the terminal exposed portion 49a of the electrode terminal 50.

[0129] On the other hand, when the upper surface of the battery housing BH is concave at its central portion, that is, in the direction toward the electrode assembly A, the upper surface of the battery housing BH and the upper surface of the terminal exposed portion 49a may be in the same plane depending on the depth of the concavity and the thickness of the terminal exposed portion 49a of the electrode terminal 50. In this case, a step may not be formed between the upper surface of the battery housing BH and the terminal exposed portion 49a.

[0130] The insulating gasket 35 is interposed between the battery housing BH and the electrode terminal 50 to prevent the battery housing BH and the electrode terminal 50 having opposite polarities from coming into contact with each other. As a result, the upper surface of the battery housing BH having a substantially flat shape can function as the second electrode terminal E2 of the cylindrical battery 1.

[0131] The insulating gasket 35 includes a gasket exposed portion 35a and a gasket insertion portion 35b. The gasket exposed portion 35a is interposed between the terminal exposed portion 49a of the electrode terminal 50 and the battery housing BH. The gasket insertion portion 35b is interposed between the terminal insertion portion 49b of the electrode terminal 50 and the battery housing BH. The gasket insertion portion 35b can be deformed together during the reveting of the terminal insertion portion 49b and be brought into close contact with the inner surface of the battery housing BH. The insulating gasket 35 can be made of, for example, a resin material having insulating properties.

[0132] Referring to FIG. 8, the gasket exposed portion 35a of the insulating gasket 35 may have a form extending so as to cover the outer peripheral surface of the terminal exposed portion 49a of the electrode terminal 50. When the insulating gasket 35 covers the outer peripheral surface of the electrode terminal 50 in this way, it is possible to prevent a short circuit from occurring in the process of coupling an electrical connection component such as a bus bar to the upper surface of the battery housing BH and / or the electrode terminal 50. Although not shown, the gasket exposed portion 35a of the insulating gasket 35 may have a form extending so as to cover not only the outer peripheral surface of the terminal exposed portion 49a but also a part of the upper surface.

[0133] When the insulating gasket 35 is made of a resin material, the insulating gasket 35 can be joined to the battery housing BH and the electrode terminal 50 by heat fusion. In this case, the airtightness at the joining interface between the insulating gasket 35 and the electrode terminal 50 and at the joining interface between the insulating gasket 35 and the battery housing BH is enhanced. On the other hand, when the gasket exposed portion 35a of the insulating gasket 35 has a form extending to the upper surface of the terminal exposed portion 49a, the electrode terminal 50 may be joined to the insulating gasket 35 by insert injection.

[0134] According to an embodiment of the present invention, the insulating gasket 35, the insulator 37, and the sealing gasket 39 may be formed of the same material, but are not necessarily limited thereto. The thickness of the insulating gasket 35 and the thickness of the insulator 37 may be the same, but are not necessarily limited thereto. When these thicknesses are different, the insulator 37 may be thinner than the insulating gasket 35, and vice versa.

[0135] On the upper surface of the battery housing BH, the entire other region excluding the regions occupied by the electrode terminal 50 and the insulating gasket 35 corresponds to the second electrode terminal E2 having a polarity opposite to that of the electrode terminal 50. In contrast, in an embodiment of the present invention, when the insulating gasket 35 is omitted and the electrode terminal 50 is partially provided with an insulating coating layer, the entire other region excluding the region occupied by the electrode terminal 50 provided with the insulating coating layer from the upper surface of the battery housing BH can function as the second electrode terminal E2.

[0136] The cylindrical side wall of the battery housing BH can be formed in one piece with the second electrode terminal E2 so that there is no discontinuous portion between them. The connection from the side wall of the battery housing BH to the second electrode terminal E2 can be a smooth curve. However, the present invention is not limited thereto, and the connection portion may include at least one edge having a predetermined angle.

[0137] Referring to FIGS. 6 to 8, the first current collector plate 36 is coupled to the upper part of the electrode assembly A. The first current collector plate 36 is made of a conductive metal material and is connected to the first electrode tab 13. Although not shown, the first current collector plate 36 may have a plurality of irregularities formed radially on its lower surface. When the irregularities are formed, the first current collector plate 36 can be pressed to push the first electrode tab 13 into the irregularities.

[0138] Referring to FIG. 9, the first current collector plate 36 is coupled to the end of the first electrode tab 13. The connection between the first electrode tab 13 and the first current collector plate 36 can be made, for example, by laser welding. The laser welding can be performed in a manner of partially melting the base material of the first current collector plate 36, or may be performed with solder for welding interposed between the first current collector plate 36 and the first electrode tab 13. In this case, it is desirable that the solder has a melting point lower than that of the first current collector plate 36 and the first electrode tab 13.

[0139] Referring to FIG. 10, the first current collector plate 36 can be coupled to a bonding surface formed by bending the end of the first electrode tab 13 in a direction parallel to the first current collector plate 36 (refer to the partial enlarged structure). The bending direction of the first electrode tab 13 can be, for example, the direction toward the winding center C of the electrode assembly A. When the first electrode tab 13 has such a bent form, the space occupied by the first electrode tab 13 can be reduced to improve the energy density. Also, the increase in the bonding area between the first electrode tab 13 and the first current collector plate 36 can achieve the effects of improving the bonding force and reducing the resistance.

[0140] Referring to FIGS. 6 to 8, the insulator 37 is provided between the upper end of the electrode assembly A and the inner surface of the battery housing BH or between the first current collector plate 36 coupled to the upper part of the electrode assembly A and the inner surface of the battery housing BH. The insulator 37 prevents contact between the first electrode tab 13 and the battery housing BH and / or between the first current collector plate 36 and the battery housing BH. Additionally, the insulator 37 may also be interposed between the upper end of the outer peripheral surface of the electrode assembly A and the inner surface of the battery housing BH. The first current collector plate 36 may be a plate extending completely across the upper end of the outer peripheral surface of the electrode assembly A. However, the present invention is not limited thereto, and the first current collector plate 36 may be formed to extend only partially across the upper end of the outer peripheral surface of the electrode assembly A.

[0141] When the cylindrical battery 1 according to an embodiment of the present invention includes the insulator 37, the terminal insertion portion 49b of the electrode terminal 50 passes through the insulator 37 and is coupled to the first current collector plate 36 or the first electrode tab 13.

[0142] The insulator 37 may include an opening adjacent to the winding center C. The terminal insertion portion 49b of the electrode terminal 50 may directly contact the first current collector plate 36 through the opening.

[0143] In an embodiment of the present invention, the terminal insertion portion 49b may have a circular planar shape, but is not limited thereto. The terminal insertion portion 49b may alternatively be polygonal, star-shaped, or have a shape with legs extending from the center, etc.

[0144] Referring to FIGS. 6 and 11, the second current collector plate 38 is coupled to the lower part of the electrode assembly A. The second current collector plate 38 is made of a conductive metal material and is connected to the second electrode tab 14. Also, the second current collector plate 38 is electrically connected to the battery housing BH. As shown in FIG. 11, the second current collector plate 38 may be interposed and fixed between the inner surface of the battery housing BH and the sealing gasket 39. Alternatively, the second current collector plate 38 may be welded to the inner wall surface of the battery housing BH.

[0145] Although not shown, the second current collector 38 may have a plurality of irregularities formed radially on one surface thereof. When the irregularities are formed, the second current collector 38 can be pressed to push the second electrode tab 14 into the irregularities.

[0146] Referring to FIG. 9, the second current collector 38 is coupled to the end of the second electrode tab 14. The coupling between the second electrode tab 14 and the second current collector 38 can be performed, for example, by laser welding. The laser welding can be performed in a manner that partially melts the base material of the second current collector 38, and may be performed with solder for welding interposed between the second current collector 38 and the second electrode tab 14. In this case, it is desirable that the solder has a melting point lower than that of the second current collector 38 and the second electrode tab 14.

[0147] Referring to FIG. 10, the second current collector 38 can be coupled to a bonding surface formed by bending the end of the second electrode tab 14 in a direction parallel to the second current collector 38 (see the partial enlarged structure). The bending direction of the second electrode tab 14 can be, for example, a direction toward the winding center C of the electrode assembly A. When the second electrode tab 14 has such a bent form, the space occupied by the second electrode tab 14 can be reduced to improve the energy density. In addition, the effect of improving the bonding force and reducing the resistance can be achieved by increasing the bonding area between the second electrode tab 14 and the second current collector 38.

[0148] Referring to FIGS. 11 and 13, the second current collector 38 may include a plurality of sub-plates 38a extending radially from the center portion and spaced apart from each other. In this case, each of the plurality of sub-plates 38a is coupled to the second electrode tab 14 and the battery housing BH.

[0149] The outer end 38b of each sub-plate 38a is bent toward the inner surface of the beading portion 23, and the end can be fixed in a state of being interposed between the sealing gasket 39 and the inner surface of the beading portion 23. Also, the end of the outer end 38b can be welded to the inner surface of the beading portion 23, for example, the lower surface. The battery housing BH and the second electrode tab 14 can be electrically connected through welding. Since the sealing gasket 39 is interposed between the cap plate 60 and the welding region of the outer end 38b, the cap plate 60 has no electrical polarity.

[0150] When the second current collector plate 38 includes a plurality of sub-plates 38a separated from each other, the second current collector plate 38 partially covers the lower surface of the electrode assembly A. Therefore, a sufficient space is secured for the gas generated in the electrode assembly A to move toward the cap plate 60, and smooth gas venting downward of the cylindrical battery 1 becomes possible. On the other hand, the structure of the second current collector plate 38 having a plurality of sub-plates 38a as described above can be similarly applied to the first current collector plate 36 described above.

[0151] Referring to FIGS. 7 and 11, a cylindrical battery 1 according to an embodiment of the present invention includes an electrode terminal 50 having a first polarity on one side in its longitudinal direction (Z-axis direction), and a second electrode terminal E2 that is electrically insulated from the electrode terminal 50 and has a second polarity. That is, in the cylindrical battery 1 according to an embodiment of the present invention, since a pair of electrode terminals (first electrode terminal E1, second electrode terminal E2) are located in the same direction, when a plurality of cylindrical batteries 1 are electrically connected, electrical connection components such as bus bars can be arranged only on one side of the cylindrical battery 1. This can lead to simplification of the battery pack structure and improvement of energy density.

[0152] In addition, the cylindrical battery 1 has a structure that enables one surface of the battery housing BH having a substantially flat form to be used as the second electrode terminal E2, thereby ensuring a sufficient bonding area when an electrical connection component such as a bus bar is bonded to the second electrode terminal E2. Thereby, the cylindrical battery 1 can ensure sufficient bonding strength between the electrical connection component and the second electrode terminal E2, and can reduce the resistance at the bonding site to a desired level.

[0153] Referring to FIG. 5, a bus bar B is connected to each of the first electrode terminal E1 and the second electrode terminal E2 of the cylindrical battery 1 according to an embodiment of the present invention. In each of the first electrode terminal E1 and the second electrode terminal E2, in order to ensure a sufficient area for the connection of the bus bar B, the width D1 of the upper surface of the region exposed outside the battery housing BH in the first electrode terminal E1, that is, the terminal exposed portion 49a, can be set to about 10% to 60% of the width D2 of the upper surface of the second electrode terminal E2, that is, the battery housing BH.

[0154] Desirably, the cylindrical battery can be a cylindrical battery having a form factor ratio (a value defined by dividing the diameter of the cylindrical battery by the height, that is, the ratio of the height h to the diameter (Φ)) greater than about 0.4.

[0155] Here, the form factor means a value indicating the diameter and height of the cylindrical battery. The cylindrical battery according to an embodiment of the present invention can be, for example, a 46110 battery, a 4875 battery, a 48110 battery, a 4880 battery, or a 4680 battery. In the numerical value indicating the form factor, the first two digits indicate the diameter of the cell, and the remaining digits indicate the height of the battery.

[0156] The battery according to an embodiment of the present invention can be a substantially cylindrical battery having a diameter of about 46 mm, a height of about 110 mm, and a form factor ratio of about 0.418.

[0157] Batteries according to other embodiments can be cylindrical batteries that are substantially cylindrical, have a diameter of about 48 mm, a height of about 75 mm, and a form factor ratio of about 0.640.

[0158] Batteries according to yet other embodiments can be cylindrical batteries that are substantially cylindrical, have a diameter of about 48 mm, a height of about 110 mm, and a form factor ratio of about 0.436.

[0159] Batteries according to yet other embodiments can be cylindrical batteries that are substantially cylindrical, have a diameter of about 48 mm, a height of about 80 mm, and a form factor ratio of about 0.600.

[0160] Batteries according to yet other embodiments can be cylindrical batteries that are substantially cylindrical, have a diameter of about 46 mm, a height of about 80 mm, and a form factor ratio of about 0.575.

[0161] Conventionally, batteries with a form factor ratio of about 0.4 or less have been used. That is, conventionally, for example, 1865 batteries, 2170 batteries, etc. have been used. In the case of an 1865 battery, the diameter is about 18 mm, the height is about 65 mm, and the form factor ratio is about 0.277. In the case of a 2170 battery, the diameter is about 21 mm, the height is about 70 mm, and the form factor ratio is about 0.300.

[0162] Referring to FIG. 14, a battery pack 3 according to an embodiment of the present invention includes an assembly of a plurality of cylindrical batteries 1 according to an embodiment of the present invention described above that are electrically connected, and a pack housing 2 that houses the same. For the sake of illustration, components such as busbars, cooling units, and power terminals for electrical connection are not shown.

[0163] Referring to FIG. 15, the vehicle 5 according to an embodiment of the present invention can be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle, and includes a battery pack 3 according to an embodiment of the present invention. The vehicle 5 includes a four-wheel vehicle or a two-wheel vehicle. The vehicle 5 operates by receiving power supply from the battery pack 3 according to an embodiment of the present invention.

[0164] The cylindrical battery according to an embodiment of the present invention may include electrode terminals 50 riveted to the bottom of the battery housing.

[0165] FIG. 16 is a cross-sectional view showing the riveting structure of the electrode terminal 50 according to an embodiment of the present invention, and FIG. 17 is an enlarged cross-sectional view of the portion indicated by the dashed-dotted circle in FIG. 16.

[0166] Referring to FIGS. 16 and 17, the riveting structure of the electrode terminal 50 according to an embodiment may include a cylindrical battery housing 51 with one side open, an electrode terminal 50 riveted through a through-hole 53 formed in the bottom 52 of the battery housing 51, and an insulating gasket 54 interposed between the electrode terminal 50 and the through-hole 53.

[0167] The battery housing 51 is made of a conductive metal material. As an example, the battery housing 51 can be made of aluminum or steel material, but the present invention is not limited thereto.

[0168] The electrode terminal 50 is made of a conductive metal material. As an example, the electrode terminal 50 can be made of aluminum, but the present invention is not limited thereto.

[0169] The insulating gasket 54 can be made of a polymer resin having insulation and elasticity. As an example, the insulating gasket 54 can be made of polypropylene, polybutylene terephthalate, polytetrafluoroethylene, etc., but the present invention is not limited thereto.

[0170] Desirably, the electrode terminal 50 includes a main body portion 50a inserted into the through hole 53, an external flange portion 50b extending along the outer surface 52a from one peripheral edge of the main body portion 50a exposed from the outer surface 52a of the bottom portion 52 of the battery housing 51, an internal flange portion 50c extending from the other peripheral edge of the main body portion 50a exposed from the inner surface 52b of the bottom portion 52 of the battery housing 51 toward the inner surface 52b, and a flat portion 50d provided inside the internal flange portion 50c.

[0171] Desirably, the flat portion 50d and the inner surface 52b of the bottom portion 52 of the battery housing 51 can be parallel. Here, "parallel" means substantially parallel when observed visually.

[0172] According to one embodiment, the angle θ between the internal flange portion 50c and the inner surface 52b of the bottom portion 52 of the battery housing 51 can be 0° to 60°. The magnitude of the angle is determined by the caulking strength when the electrode terminal 50 is attached to the through hole 53 of the battery housing 51 by a caulking method. As an example, the angle θ can decrease to 0° as the caulking strength increases. If the angle exceeds 60°, the sealing effect of the insulating gasket 54 may decrease.

[0173] According to another embodiment, between the internal flange portion 50c and the flat portion 50d Indentation a portion 55 can be provided. Indentation The portion 55 can have a cross-sectional structure of an asymmetric groove. As an example, the asymmetric groove can be substantially V-shaped. The asymmetric groove can include a side wall 55a of the flat portion 50d and an inclined surface 55b of the internal flange portion 50c connected to an end of the side wall 55a. The side wall 55a can be substantially perpendicular to the inner surface 52b of the bottom portion 52 of the battery housing 51. "Perpendicular" means substantially perpendicular when observed visually. Indentation The portion 55 is formed by the shape of a caulking jig when the electrode terminal 50 is attached to the through hole 53 of the battery housing 51 by a caulking method.

[0174] Desirably, the thickness of the inner flange portion 50c may decrease as it is farther from the main body portion 50a of the electrode terminal 50.

[0175] According to another form, the insulating gasket 54 may include an external gasket 54a interposed between the external flange portion 50b and the outer surface 52a of the bottom 52 of the battery housing 51, and an internal gasket 54b interposed between the inner flange portion 50c and the inner surface 52b of the bottom 52 of the battery housing 51.

[0176] The thickness of the external gasket 54a and the internal gasket 54b may vary depending on the position. Desirably, the thickness of the region interposed between the inner edge 56 of the through hole 53 connected to the inner surface 52b of the bottom 52 of the battery housing 51 and the inner flange portion 50c in the region of the internal gasket 54b may be relatively small. Desirably, a minimum thickness point may exist in the gasket region interposed between the inner edge 56 of the through hole 53 and the inner flange portion 50c. Also, the inner edge 56 of the through hole 53 may include a facing surface 57 facing the inner flange portion 50c.

[0177] On the other hand, the upper and lower ends of the inner wall of the through hole 53 perpendicular to the bottom 52 of the battery housing 51 are chamfered so as to form a tapered surface toward the electrode terminal 50. However, the upper and / or lower ends of the inner wall of the through hole 53 may be deformed into a smooth curved surface having a curvature. In this case, the stress applied to the insulating gasket 54 near the upper and / or lower ends of the inner wall of the through hole 53 can be further relaxed.

[0178] Desirably, the internal gasket 54b may extend longer than the inner flange portion 50c while making an angle of 0° to 60° with the inner surface 52b of the bottom 52 of the battery housing 51.

[0179] In yet another form, based on the inner surface 52b of the bottom 52 of the battery housing 51, the height H1 of the flat portion 50d can be the same as or greater than the height H2 of the end of the internal gasket 54b. Also, based on the inner surface 52b of the bottom 52 of the battery housing 51, the height H1 of the flat portion 50d can be the same as or greater than the height H3 of the end of the internal flange portion 50c.

[0180] When the height parameters H1, H2, and H3 satisfy the above conditions, interference between the internal flange portion 50c and the internal gasket 54b with other components can be prevented.

[0181] In yet another form, the radius R1 from the center of the main body portion 50a of the electrode terminal 50 to the periphery of the external flange portion 50b can be 10% to 60% based on the radius R2 of the bottom 52 of the battery housing 51.

[0182] When R1 becomes smaller, the welding space becomes insufficient when welding an electrical wiring component (bus bar) to the electrode terminal 50. Also, when R1 becomes larger, the welding space decreases when welding an electrical wiring component (bus bar) to the outer surface 52a of the bottom 52 of the battery housing 51 excluding the electrode terminal 50.

[0183] By adjusting the ratio R1 / R2 to be 10% to 60%, an appropriate welding space for the electrode terminal 50 and the outer surface of the bottom 52 of the battery housing 51 can be ensured.

[0184] Also, the radius R3 from the center of the main body portion 50a of the electrode terminal 50 to the periphery of the flat portion 50d can be 4% to 30% based on the radius R2 of the bottom 52 of the battery housing 51.

[0185] When R3 becomes small, the welding space becomes insufficient when welding the current collector plate (refer to 79 in FIG. 18) to the flat portion 50d of the electrode terminal 50, and the welding area of the electrode terminal 50 may decrease and the contact resistance may increase. Also, R3 must be smaller than R1. When R3 becomes large, the inner flange portion 50c becomes thin and the force with which the inner flange portion 50c presses the insulating gasket 54 becomes weak, and the sealing ability of the insulating gasket 54 may decrease.

[0186] When adjusting R3 / R2 at 4% - 30%, not only can the welding process be easily carried out by sufficiently ensuring the welding area between the flat portion 50d of the electrode terminal 50 and the current collector plate (79 in FIG. 18), but also the contact resistance in the welding region can be decreased, and a decrease in the sealing ability of the insulating gasket 54 can be prevented.

[0187] According to an embodiment of the present invention, the riveting structure of the electrode terminal 50 can be formed using a caulking jig that moves up and down. First, a preform (not shown) of the electrode terminal 50 is inserted through a through hole 53 formed in the bottom 52 of the battery housing 51 with an insulating gasket 54 interposed therebetween. A preform refers to an electrode terminal before being riveted.

[0188] Thereafter, the caulking jig is inserted into the inner space of the battery housing 51. The caulking jig has grooves and protrusions corresponding to the final shape of the electrode terminal 50 on the surface facing the preform in order to rivet the preform to form the electrode terminal 50.

[0189] Next, the caulking jig is moved downward to press-mold the upper portion of the preform, deforming the preform into the riveted electrode terminal 50.

[0190] While the preform is being pressurized by the caulking jig, the outer gasket 54a interposed between the outer flange portion 50b and the outer surface 52a of the bottom 52 of the battery housing 51 is elastically compressed and its thickness decreases. Also, the thickness of the inner gasket 54b portion interposed between the inner edge 56 of the through hole 53 and the preform decreases further than other regions while being elastically compressed by the inner flange portion 50c. In particular, the region where the thickness of the inner gasket 54b decreases intensively is the portion indicated by the dashed-dotted circle in Fig. 17. Thereby, the sealing performance and airtightness between the riveted electrode terminal 50 and the battery housing 51 are remarkably improved.

[0191] Preferably, the insulating gasket 54 is not physically damaged during the process of the preform being riveted, and is preferably sufficiently compressed so as to ensure a desired sealing strength.

[0192] As an example, when the insulating gasket 54 is made of polybutylene terephthalate, it is desirable that the compression ratio of the insulating gasket 54 at the point where it is compressed to the minimum thickness is 50% or more. The compression ratio is the ratio of the thickness change before and after compression to the thickness before compression.

[0193] As another example, when the insulating gasket 54 is made of polytetrafluoroethylene, it is desirable that the compression ratio of the insulating gasket 54 at the point where it is compressed to the minimum thickness is 60% or more.

[0194] As still another example, when the insulating gasket 54 is made of polypropylene, it is desirable that the compression ratio of the insulating gasket 54 at the point where it is compressed to the minimum thickness is 60% or more.

[0195] Desirably, by performing the vertical movement of the caulking jig at least twice, the pressure forming of the upper part of the preform can be performed step by step. That is, the preform can be pressure-formed step by step and deformed in several steps. At this time, the pressure applied to the caulking jig may be increased step by step. By doing so, by dispersing the stress applied to the preform in several steps, it is possible to prevent the insulating gasket 54 from being damaged during the caulking process. In particular, when the internal gasket 54b portion interposed between the inner edge 56 of the through hole 53 and the preform is intensively compressed by the internal flange portion 50c, the damage to the gasket is minimized.

[0196] After the pressure forming of the preform using the caulking jig is completed and the caulking jig is removed from the battery housing 51, as shown in FIG. 17, the riveting structure of the electrode terminal 50 according to the embodiment of the present invention is obtained.

[0197] According to the above-described embodiment, the caulking jig pressure-forms the upper part of the preform through vertical movement inside the battery housing 51. In some cases, a rotary rotating jig used in the prior art may be used for the pressure forming of the preform.

[0198] However, the rotary rotating jig rotates in a state inclined by a predetermined angle with respect to the central axis of the battery housing 51. Therefore, a rotary rotating jig with a large rotation radius may interfere with the inner wall of the battery housing 51. Also, when the battery housing 51 is deep, the length of the rotary rotating jig also becomes correspondingly long. In this case, the rotation radius of the end portion of the rotary rotating jig becomes large, and the pressure forming of the preform may not be performed sufficiently. Therefore, the pressure forming using the caulking jig is more effective than the method using the rotary rotating jig.

[0199] The riveting structure of the electrode terminal 50 according to the above-described embodiment of the present invention is applicable to a cylindrical battery.

[0200] FIG. 18 is a cross-sectional view of a cylindrical battery 70 cut along the longitudinal direction (Y-axis direction) according to an embodiment of the present invention.

[0201] Referring to FIG. 18, a cylindrical battery 70 according to an embodiment includes a jelly roll type electrode assembly 71 in which a sheet-like first electrode and a second electrode are wound with a separator interposed therebetween, a first plain portion 72 of the first electrode is exposed at the upper part, and a second plain portion 73 of the second electrode is exposed at the lower part.

[0202] In the embodiment, the first electrode may be a positive electrode and the second electrode may be a negative electrode. Of course, the opposite case is also possible.

[0203] The winding method of the electrode assembly 71 is substantially the same as the winding method of the electrode assembly used in the manufacture of the tabless cylindrical battery according to the prior art described with reference to FIG. 2.

[0204] In the illustration of the electrode assembly 71, only the first plain portion 72 and the second plain portion 73 that are exposed and extend outside the separator are shown in detail, and the illustration of the winding structure of the first electrode, the second electrode, and the separator is omitted.

[0205] Further, the cylindrical battery 70 includes a cylindrical battery housing 51 that houses the electrode assembly 71 and is electrically connected to the second plain portion 73 of the second electrode.

[0206] Preferably, one side (lower part) of the battery housing 51 is open. Also, the bottom 52 of the battery housing 51 has a structure in which the electrode terminal 50 is riveted to the through hole 53 through a caulking process.

[0207] Specifically, the electrode terminal 50 may include a main body portion 50a inserted into the through hole 53, an external flange portion 50b extending along the outer surface 52a from one peripheral edge of the main body portion 50a exposed from the outer surface 52a of the bottom portion 52 of the battery housing 51, an internal flange portion 50c extending from the other peripheral edge of the main body portion 50a exposed from the inner surface 52b of the bottom portion 52 of the battery housing 51 toward the inner surface 52b, and a flat portion 50d provided inside the internal flange portion 50c.

[0208] Further, the cylindrical battery 70 may include an insulating gasket 54 interposed between the electrode terminal 50 and the through hole 53.

[0209] Further, the cylindrical battery 70 may include a sealing body 74 that seals the open end of the battery housing 51 in an insulating manner. Desirably, the sealing body 74 may include a non-polar cap plate 74a and a sealing gasket 74b interposed between the peripheral edge of the cap plate 74a and the open end of the battery housing 51.

[0210] The cap plate 74a may be made of a conductive metal material such as aluminum, steel, or nickel. Further, the sealing gasket 74b may be made of polypropylene, polybutylene terephthalate, polytetrafluoroethylene, etc. having insulation and elasticity. However, the present invention is not limited by the materials of the cap plate 74a and the sealing gasket 74b.

[0211] The cap plate 74a may include a venting portion 77 that ruptures when the internal pressure of the battery housing 51 exceeds a critical value. The venting portion 77 may be a groove formed through notching. The venting portion 77 may be formed on both surfaces of the cap plate 74a. The venting portion 77 may form a continuous or discontinuous circular pattern, linear pattern, or other pattern on the surface of the cap plate 74a.

[0212] The battery housing 51 may include a crimping portion 75 that extends and is bent inside the battery housing 51 to fix the sealing body 74, wraps around and fixes the peripheral edge of the cap plate 74a together with the sealing gasket 74b.

[0213] Also, the battery housing 51 may include a beading portion 76 that is pushed inside the battery housing 51 in a region adjacent to the open end. The beading portion 76 supports the peripheral edge of the sealing body 74, particularly the outer peripheral surface of the sealing gasket 74b, when the sealing body 74 is fixed by the crimping portion 75.

[0214] Also, the cylindrical battery 70 may include a first current collector plate 78 that is welded to the plain portion 72 of the first electrode. Desirably, at least a part of the first current collector plate 78, for example, the central portion 79a, may be welded to the flat portion 50d of the electrode terminal 50.

[0215] Desirably, when welding the first current collector plate 78, the welding tool may be inserted through a cavity 80 present in the core of the electrode assembly 71 to reach the welding point of the first current collector plate 78. Also, when the first current collector plate 78 is welded to the flat portion 50d of the electrode terminal 50, since the electrode terminal 50 supports the welding region of the first current collector plate 78, a strong pressure can be applied to the welding region to improve the welding quality. Also, since the flat portion 50d of the electrode terminal 50 has a large area, a wide welding region can be ensured. Thereby, by reducing the contact resistance of the welding region, the internal resistance of the cylindrical battery 70 can be reduced. The face-to-face welding structure between the riveted electrode terminal 50 and the first current collector plate 78 is very useful for rapid charging using a high C-rate current. This is because the current density per unit area in the cross-section in the direction of current flow can be reduced, and thus the amount of heat generated in the current path can be reduced more than before.

[0216] When welding the flat portion 50d of the electrode terminal 50 and the first current collector plate 78, any one of laser welding, ultrasonic welding, spot welding, and resistance welding can be used. The area of the flat portion 50d can be adjusted according to the welding method, but it is preferably 2 mm or more for welding strength and ease of the welding process.

[0217] As an example, when the flat portion 50d and the first current collector plate 78 are welded by laser and welded in a continuous or discontinuous line of an arc pattern, the diameter of the flat portion 50d is preferably 4 mm or more. When the diameter of the flat portion 50d satisfies the corresponding conditions, the welding strength can be ensured, and there is no difficulty in the process of inserting a laser welding tool into the cavity 80 of the electrode assembly 71 for welding.

[0218] As another example, when the flat portion 50d and the first current collector plate 78 are welded by ultrasonic and welded in a circular pattern, the diameter of the flat portion 50d is preferably 2 mm or more. When the diameter of the flat portion 50d satisfies the corresponding conditions, the welding strength can be ensured, and there is no difficulty in the process of inserting an ultrasonic welding tool into the cavity 80 of the electrode assembly 71 for welding.

[0219] Further, the cylindrical battery 70 may further include a second current collector plate 79 that is welded to the second plain portion 73 of the second electrode. The second current collector plate 79 is made of a conductive metal material such as aluminum, steel, or nickel. Desirably, at least a part 79a of the periphery of the second current collector plate 79 that does not contact the second plain portion 73 of the second electrode can be interposed between the beading portion 76 and the sealing gasket 74b and fixed by the crimping portion 75. Optionally, at least a part 79a of the periphery of the second current collector plate 79 can be fixed by welding to the inner peripheral surface 76a of the beading portion 76 adjacent to the crimping portion 75.

[0220] Further, the cylindrical battery 70 may further include an insulator 80. The insulator 80 may be interposed between the first current collector 78 and the inner surface 52b of the bottom 52 of the battery housing 51, and between the inner peripheral surface 51a of the side wall of the battery housing 51 and the electrode assembly 71. Desirably, the insulator 80 includes a welding hole 80a that exposes the flat portion 50d of the electrode terminal 50 to the side of the first current collector 78, and may cover the surface of the first current collector 78 and the periphery of one side (upper part) of the electrode assembly 71.

[0221] Desirably, the first non-coated portions 72 and the second non-coated portions 73 of the first electrode and / or the second electrode can form bent surfaces at the upper and lower portions of the electrode assembly 71 by being bent from the outer peripheral side to the core side of the electrode assembly 71. Further, the first current collector 78 is welded to the bent surface formed while the first non-coated portion 72 of the first electrode is being bent, and the second current collector 79 can be welded to the bent surface formed while the second non-coated portion 73 of the second electrode is being bent.

[0222] In order to relieve the stress generated when the first non-coated portion 72 and the second non-coated portion 73 are bent, the first electrode and / or the second electrode may have an improved structure different from that of a conventional electrode (see FIG. 1).

[0223] FIG. 19 is a plan view exemplarily showing the structure of an electrode 90 according to a desirable embodiment of the present invention.

[0224] Referring to FIG. 19, the electrode 90 includes a sheet-like current collector 91 made of a foil of a conductive material, an active material layer 92 formed on at least one surface of the current collector 91, and a non-coated portion 93 where the active material is not coated at the long side end of the current collector 91.

[0225] Desirably, the blank portion 93 may include a plurality of segmented pieces 93a that are notched. The plurality of segmented pieces 93a form a plurality of groups, and the segmented pieces 93a belonging to each group may have the same height (length in the Y direction) and / or width (length in the X direction) and / or separation pitch. The number of segmented pieces 93a belonging to each group may be increased or decreased compared to the illustration. The segmented piece 93a may be trapezoidal, but may be deformed into a square, parallelogram, semi-circular or semi-elliptical shape, etc.

[0226] Desirably, the height of the segmented piece 93a may increase stepwise from the core side towards the outer peripheral side. Also, the core-side blank portion 93' adjacent to the core side may not include the segmented piece 93a, and the height of the core-side blank portion 93' may be lower than that of other blank portion regions.

[0227] Optionally, the electrode 90 may include an insulating coating layer 94 that covers the boundary between the active material layer 92 and the blank portion 93. The insulating coating layer 94 includes an insulating polymer resin and may optionally further include an inorganic filler. The insulating coating layer 94 prevents the end of the active material layer 92 from contacting the active material layer of the opposite polarity facing through the separator, and plays a role of structurally supporting the bending of the segmented piece 93a. Therefore, when the electrode 90 is wound as an electrode assembly, it is desirable that at least a part of the insulating coating layer 94 is exposed to the outside from the separator.

[0228] FIG. 20 is a cross-sectional view of an electrode assembly 100 in which the blank portion cutting structure of the electrode 90 according to an embodiment of the present invention is applied to a first electrode and a second electrode, cut along the longitudinal direction (Y-axis direction).

[0229] Referring to FIG. 20, the electrode assembly 100 can be manufactured by the winding method described with reference to FIG. 2. For convenience of explanation, the protruding structures of the first blank portion 72 and the second blank portion 73 extending outside the separator are shown in detail, and the illustration of the winding structure of the first electrode, the second electrode, and the separator is omitted. The first blank portion 72 protruding upward extends from the first electrode, and the second blank portion 73 protruding downward extends from the second electrode.

[0230] The patterns in which the heights of the first non-coated portion 72 and the second non-coated portion 73 change are schematically illustrated. That is, depending on the cutting position of the cross-section, the heights of the first non-coated portion 72 and the second non-coated portion 73 may change irregularly. As an example, if the side portion of the trapezoidal segment 93a is cut, the height of the non-coated portion in the cross-section becomes lower than the height of the segment 93a. Therefore, it should be understood that the heights of the first non-coated portion 72 and the second non-coated portion 73 shown in the drawing showing the cross-section of the electrode assembly 100 correspond to the average of the heights of the non-coated portions included in the respective winding turns.

[0231] As shown in FIG. 21, the first non-coated portion 72 and the second non-coated portion 73 can be bent from the outer peripheral side to the core side of the electrode assembly 100. In FIG. 20, the bent portion 101 is indicated by a dashed box. When the first non-coated portion 72 and the second non-coated portion 73 are bent, bending surfaces 102 are formed at the upper and lower portions of the electrode assembly 100 while the segments adjacent in the radial direction overlap multiplicatively. At this time, the core-side non-coated portion (93' in FIG. 19) has a low height and is not bent, and the height h of the segment bent on the innermost side is the same as or smaller than the radial length r of the winding region formed by the core-side non-coated portion 93' without a segment structure. Therefore, the cavity 80 in the core of the electrode assembly 100 is not closed by the bent segments. If the cavity 80 is not closed, there is no problem in the electrolyte injection process, and the efficiency of electrolyte injection is improved. Also, a welding tool can be inserted through the cavity 80 to easily perform welding between the electrode terminal 50 and the first current collector plate 78.

[0232] In the cylindrical battery 70 according to the embodiment of the present invention, the cap plate 74a of the sealing body 74 has no polarity. Instead, since the second current collector plate 79 is connected to the side wall of the battery housing 51, the outer surface 52a of the bottom 52 of the battery housing 51 has the opposite polarity to the electrode terminal 50. Therefore, when connecting a plurality of batteries in series and / or in parallel, wiring such as bus bar connection can be performed at the upper part of the cylindrical battery 70 using the outer surface 52a of the bottom 52 of the battery housing 51 and the electrode terminal 50. As a result, the number of batteries that can be mounted in the same space can be increased, and the energy density can be improved.

[0233] Hereinafter, an embodiment of the positive electrode active material used in the cylindrical battery according to an embodiment of the present invention will be described.

[0234] In the embodiment, the "primary particle" means a particle unit in which no grain boundary is present in appearance when observed at a magnification of 5,000 to 20,000 times using a scanning electron microscope (SEM) or an electron backscatter diffraction (EBSD) pattern analyzer. The "average particle size of primary particles" means the arithmetic average value calculated after measuring the particle sizes of the primary particles observed in the SEM or EBSD image.

[0235] The "secondary particle" is a particle formed by aggregation of a plurality of primary particles. In the present invention, in order to distinguish from the conventional secondary particles formed by aggregation of several tens to several hundreds of primary particles, the secondary particles formed by aggregation of 10 or less primary particles will be referred to as pseudo single particles.

[0236] In the present invention, the "specific surface area" is measured by the BET method, and specifically, it can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using Belsorp-mini II manufactured by Nippon Bell Co., Ltd.

[0237] 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 is the minimum particle size in the volume cumulative distribution, and D 50 is the particle size when the volume cumulative amount is 50%, and D max is the maximum particle size in the volume cumulative distribution. When the positive electrode active material is single particles, D 50 means the average particle diameter of the primary particles. Also, when the positive electrode active material is pseudo single particles, D 50 means the average particle diameter of the particles formed by aggregation of the primary particles.

[0238] 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 and then introducing it into a commercially available laser diffraction particle size measuring device (for example, MT3000 manufactured by Microtrac), irradiating it with ultrasonic waves of about 28 kHz at an output of 60 W, and then obtaining and measuring a volume cumulative particle size distribution graph.

[0239] In the present invention, "consisting essentially of A" means including the A component and any component not mentioned that does not substantially affect the basic and novel features of the present invention. The basic and novel features of the present invention include at least one of minimizing particle cracking during battery manufacturing, minimizing the gas generated by such particle cracking, and minimizing the occurrence of internal cracks. A person of ordinary skill in the art can recognize the material effects of such characteristics.

[0240] As a result of repeated research to develop a positive electrode for an electrochemical device with excellent safety while achieving high capacity and an electrochemical device including the same, the present inventors confirmed that when using, alone, a positive electrode active material in the form of single particles consisting of 1 or pseudo single particles which are aggregates of 10 or less primary particles as the positive electrode active material, the safety of a large cylindrical battery can be significantly improved.

[0241] According to one embodiment, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on at least one side surface of the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, and optionally may include a conductive material and / or a binder.

[0242] The positive electrode may have a structure in which a positive electrode active material layer is formed on at least one surface or both surfaces of a long sheet-like positive electrode current collector. The positive electrode active material layer may include a positive electrode active material and a binder.

[0243] Specifically, the positive electrode can be manufactured by applying a positive electrode slurry, which is prepared by dispersing a positive 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 surface or both surfaces of a long sheet-like positive electrode current collector, removing the solvent of the positive electrode slurry through a drying process, and then rolling. On the other hand, a positive electrode including a non-coated portion can be manufactured by a method of not applying the positive electrode slurry to a partial region of the positive electrode current collector, for example, one end of the positive electrode current collector, when applying the positive electrode slurry.

[0244] In another embodiment, the positive electrode active material includes single-particle system active material particles. In one embodiment, the single-particle system active material particles may be included at 90 wt% or more, 95 wt% or more, 98 wt% or more, or 99 wt% or more based on 100 wt% of the positive electrode active material. In a specific embodiment, the positive electrode active material may be composed only of the single-particle system active material particles.

[0245] In this specification, the single-particle system active material particles refer to those that include all single particles, pseudo-single particles, or both. The single particle is a particle composed of one primary particle, and the pseudo-single particle is an aggregate of 10 or fewer primary particles.

[0246] Conventionally, as the positive electrode active material of a lithium battery, spherical secondary particles aggregated from dozens to hundreds of primary particles have generally been used. However, in the case of a positive electrode active material in the form of secondary particles in which many primary particles are aggregated in this way, the primary particles are likely to fall off and particle cracking is likely to occur during the rolling process in the production of the positive electrode, and there is a problem that cracks occur inside the particles during the charge and discharge process. When particle cracking or cracks inside the particles of the positive electrode active material occur, the contact area with the electrolytic solution increases, so there is a problem that gas generation due to side reactions with the electrolytic solution increases. If gas generation increases inside a cylindrical battery, there is a risk that the internal pressure of the battery increases and the battery explodes. In particular, when increasing the volume of a cylindrical battery, the amount of active material inside the battery increases due to the volume increase, and as a result, the amount of gas generation also increases significantly, so the risk of ignition and / or explosion of the battery becomes even greater.

[0247] On the other hand, single-particle active material particles in the form of single particles composed of one primary particle or pseudo-single particles aggregated from 10 or fewer primary particles have higher particle strength than conventional positive electrode active materials in the form of secondary particles in which dozens to hundreds of primary particles are aggregated, so particle cracking hardly occurs during rolling. Also, in the case of single-particle active material particles, since the number of primary particles constituting the particles is small, there are few changes due to volume expansion and contraction of the primary particles during charge and discharge, and as a result, the generation of cracks inside the particles is also significantly reduced.

[0248] Therefore, when using single-particle active material particles as in one embodiment of the present invention, the amount of gas generation due to particle cracking and internal cracks can be significantly reduced. As a result, when applied to a large cylindrical battery, excellent safety can be realized.

[0249] On the other hand, it is desirable that the single particles and / or pseudo-single particles are contained in an amount of 95 wt% to 100 wt%, preferably 98 wt% to 100 wt%, more preferably 99 wt% to 100 wt%, and even more preferably 100 wt% based on the weight of the total positive electrode active material contained in the positive electrode.

[0250] 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. When the secondary particle form of the positive electrode active material is contained in an amount exceeding 5 wt% in the total positive electrode active material, side reactions with the electrolyte increase due to fine powder generated from the secondary particles during the manufacture of the electrode and during charge and discharge, resulting in a decrease in the effect of suppressing gas generation, and thus a decrease in the effect of improving stability when applied to large batteries.

[0251] On the other hand, the positive electrode active material containing single particles and / or pseudo single particles according to an embodiment of the present invention has a D min that can be 1.0 μm or more, 1.1 μm or more, 1.15 μm or more, 1.2 μm or more, 1.25 μm or more, 1.3 μm or more, or 1.5 μm or more. When the D min of the positive electrode active material is less than 1.0 μm, the linear pressure increases in the rolling process of the positive electrode, and particle cracking is likely to occur, resulting in a decrease in thermal stability and insufficient thermal stability can be ensured when applied to large cylindrical batteries.

[0252] On the other hand, considering the resistance and output characteristics, the D min of the positive electrode active material can be 3 μm or less, 2.5 μm or less, or 2 μm or less. If the D min is too large, the lithium ion diffusion distance inside the particles increases, and there is a risk of a decrease in resistance and output characteristics.

[0253] For example, the D min of the positive electrode active material can be 1.0 μm to 3 μm, 1.0 μm to 2.5 μm, or 1.3 μm to 2.0 μm.

[0254] On the other hand, the positive electrode active material can have a D 50 that is 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, more preferably 2 μm to 5 μm.

[0255] The cathode active material in single-particle and / or pseudo-single-particle form has a problem that the lithium ion mobility is lower than that of the cathode active material in secondary particle form and the resistance increases because there are few interfaces between primary particles that serve as diffusion paths of lithium ions inside the particles. Such an increase in resistance becomes more severe as the particle size increases, and an increase in resistance affects the capacity and output characteristics adversely. Therefore, by adjusting D 50 of the cathode active material to 5 μm or less, an increase in resistance can be suppressed by minimizing the lithium ion diffusion distance inside the particles of the cathode active material.

[0256] Also, the cathode active material may have D max of 12 μm to 17 μm, preferably 12 μm to 16 μm, more preferably 12 μm to 15 μm. When D max of the cathode active material satisfies the above range, the resistance characteristics and capacity characteristics are further excellent. When D max of the cathode active material is too large, it is a case where aggregation occurs between single particles, and the lithium ion migration path inside the aggregated particles becomes long and the lithium ion mobility decreases, which may increase the resistance. On the other hand, when D max of the cathode active material is too small, it is a case where excessive crushing is performed, and D min may become less than 1 μm due to excessive crushing, so there is a risk that particle cracking during rolling is induced and the thermal stability decreases.

[0257] On the other hand, the cathode active material may have a particle size distribution (PSD) represented by the following formula (1) of 3 or less, preferably 2 to 3, more preferably 2.3 to 3. [Formula 1] Particle size distribution (PSD) = (D max - D min ) / D 50

[0258] When the cathode active material has the above particle size distribution, the electrode density of the cathode can be appropriately maintained, and particle cracking and an increase in resistance can be effectively suppressed.

[0259] On the one hand, the average particle size of the primary particles of the positive electrode active material can be 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less, and for example, it can be 0.5 μm to 5 μm, desirably 1 μm to 5 μm, more desirably 2 μm to 5 μm. When the average particle size of the primary particles satisfies the above range, it is possible to form a positive electrode active material in the form of single particles and / or pseudo-single particles with excellent electrochemical properties. 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, and the effect of suppressing particle cracking during rolling may decrease. On the other hand, if the average particle size of the primary particles is too large, the lithium diffusion path inside the primary particles becomes long, the resistance increases, and the output characteristics may decrease.

[0260] In one embodiment of the present invention, it is desirable 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, a bimodal positive electrode active material obtained by mixing a large particle size positive electrode active material with a large average particle size and a small particle size positive electrode active material with a small average particle size has been widely used. However, in the case of a positive electrode active material in the form of single particles or pseudo-single particles, as the particle size increases, the lithium migration path becomes long and the resistance increases significantly. Therefore, when large particle size particles are mixed and used, there is a problem that the capacity and output characteristics may decrease. Therefore, in the present invention, by using a positive electrode active material having a unimodal distribution, an increase in resistance can be minimized.

[0261] On the one hand, the positive electrode active material may contain a lithium nickel-based oxide, and specifically, it may contain a lithium nickel-based oxide containing 80 mol% or more of Ni based on the total number of moles of transition metals. Desirably, the lithium nickel-based oxide may contain Ni in an amount of 80 mol% or more and less than 100 mol%, 82 mol% or more and less than 100 mol%, or 83 mol% or more and less than 100 mol%. When a lithium nickel-based oxide with a high Ni content as described above is used, a high capacity can be realized.

[0262] More specifically, the positive electrode active material may contain 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 In Chemical Formula 1, the M 1 may be Mn, Al, or a combination thereof, desirably Mn, or Mn and Al.

[0263] The M 2 is one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, desirably one or more selected from the group consisting of Zr, Y, Mg, and Ti, and more desirably Zr, Y, or a combination thereof. The M 2 element is not necessarily included, but when included in an appropriate amount, it can play a role in promoting particle growth during firing or improving the stability of the crystal structure.

[0264] The a represents the lithium molar ratio in the lithium nickel-based oxide, and may be 0.8 ≤ a ≤ 1.2, 0.85 ≤ a ≤ 1.15, or 0.9 ≤ a ≤ 1.2. When the lithium molar ratio satisfies the above range, a stable crystal structure of the lithium nickel-based oxide can be formed.

[0265] The b represents the nickel molar ratio in the total metal excluding lithium in the lithium nickel-based oxide, and may 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 nickel molar ratio satisfies the above range, a high energy density can be shown and a high capacity can be realized.

[0266] Said c represents the molar ratio of cobalt in the total metal excluding 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.

[0267] Said d represents the molar ratio of element M in the total metal excluding lithium in the lithium nickel-based oxide 1 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 element M 1 satisfies the above range, the structural stability of the positive electrode active material is excellent.

[0268] Said e represents the molar ratio of element M in the total metal excluding lithium in the lithium nickel-based oxide 2 and can be 0 ≤ e ≤ 0.1 or 0 ≤ e ≤ 0.05.

[0269] On the other hand, the positive electrode active material according to an embodiment of the present invention may further include, if necessary, a coating layer containing 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 on the surface of the lithium nickel-based oxide particles. Desirably, the coating element can be Al, B, Co, or a combination thereof.

[0270] When a coating layer is present on the surface of the lithium nickel-based oxide particles, the contact between the electrolyte and the lithium nickel-based oxide is suppressed by the coating layer, and thereby the effect of reducing the elution of transition metals or gas generation due to the side reaction with the electrolyte can be obtained.

[0271] The positive electrode active material may be contained in an amount of 80 wt% to 99 wt%, desirably 85 wt% to 99 wt%, more desirably 90 wt% to 99 wt% based on the total weight of the positive electrode active material layer.

[0272] On the other hand, as the positive electrode current collector, various positive electrode current collectors used in the art may be used. For example, as the positive electrode current collector, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may usually have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to enhance the adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc.

[0273] On the other hand, in one embodiment of the present invention, all or part of the single-particle active material particles may have a core-shell structure in which the surface of the particles is coated with a conductive coating layer. The conductive coating layer may cover at least part or all of the particles. The conductive coating layer contains a conductive nanomaterial.

[0274] In the case of the single-particle active material particles, there is a problem that the resistance is higher and the contact area with the conductive material is smaller than that of the conventional secondary particle-shaped positive electrode active material, so the electrical conductivity decreases. If an excessive amount of the conductive material is added to improve the electrical conductivity, aggregation occurs in the positive electrode slurry and the viscosity increases, thereby causing a problem of reduced coating properties. Therefore, in order to achieve smooth coating properties, it is necessary to reduce the solid content to lower the viscosity of the positive electrode slurry. However, if the solid content in the positive electrode slurry decreases, the content of the active material decreases, resulting in a problem of reduced capacity characteristics. In order to solve such problems, the present invention enables excellent electrical conductivity to be realized without adding a separate conductive material to the positive electrode slurry by coating the surface of the single-particle active material particles with a conductive nanomaterial.

[0275] In an embodiment of the present invention, when applying a positive electrode active material in which a conductive nanomaterial is coated on the surface of the single-particle-based active material particles, the positive electrode active material layer may not use a conductive material in a portion excluding the conductive coating layer. In this way, since it is not necessary to additionally use a conductive material that induces aggregation of the positive electrode slurry, the viscosity of the positive electrode slurry is reduced, the content of the solid component is increased, and the processability of the electrode coating and the electrode adhesion can be improved.

[0276] The conductive nanomaterial has a nano-size so as to be smoothly coated on the particles, and may be any material having conductivity, and its type is not particularly limited. For example, the conductive nanomaterial may be a carbon nanotube, a carbon nanoparticle, or the like.

[0277] The conductive nanomaterial can have various forms, and may be, for example, spherical, flaky, or fibrous.

[0278] On the other hand, the conductive coating layer can be formed by a heat treatment method after mixing the single-particle-based active material particles as the core part and the conductive nanomaterial. At this time, the mixing can be performed by solid-phase mixing or liquid-phase mixing.

[0279] In an embodiment of the present invention, the positive electrode active material layer contains flaky graphite. When the single-particle-based active material is used as the positive electrode active material, when the positive electrode active material layer contains flaky graphite, when the positive electrode active material layer is rolled, the flaky graphite provides a sliding effect to the positive electrode active material, improving the rolling characteristics of the electrode and reducing the porosity of the electrode to a target level. Thereby, the battery to which the positive electrode according to an embodiment of the present invention is applied can have improved stability, initial resistance characteristics, and charge-discharge efficiency.

[0280] In an embodiment of the present invention, the flaky graphite may be contained in an amount of 0.1 wt% to 5 wt%, preferably 0.1 wt% to 3 wt%, based on 100 wt% of the positive electrode active material layer.

[0281] When the content of the flaky graphite satisfies the above range, the rolling characteristics of the positive electrode can be improved to achieve excellent electrode density. If the content of the flaky graphite is small, the improvement effect of the rolling characteristics is low. If it is excessive, it may induce an increase in the slurry viscosity and a decrease in the phase stability, and the electrode uniformity may decrease due to the combination with the conductive material, and the resistance may increase.

[0282] On the other hand, the flaky graphite used in the present invention may have an average particle size of 1 μm to 20 μm, preferably 2 μm to 10 μm, more preferably 3 μm to 5 μm, but is not limited thereto. If the flaky graphite is too small, it is difficult to achieve the desired porosity, and the current density may be reduced and the capacity may decrease. At this time, the average particle size of the flaky graphite can be measured by the laser diffraction method (ISO 13320).

[0283] In addition, the flaky graphite may have an aspect ratio of 0.1 to 500, preferably 1 to 100, more preferably 1 to 30. When the aspect ratio of the flaky graphite satisfies the above range, it has the effect of improving the conductivity and reducing the electrode resistance.

[0284] In addition, the flaky graphite has a density of 2.0 g / cm 3 ~2.5 g / cm 3 , preferably 2.1 g / cm 3 ~2.4 g / cm 3 , more preferably 2.2 g / cm 3 ~2.3 g / cm 3 and may be.

[0285] On the other hand, in one embodiment of the present invention, the porosity of the positive electrode active material layer may be 15% to 23%, preferably 17% to 23%, more preferably 18% to 23%. When the porosity of the positive electrode active material layer satisfies the above range, the electrode density can be increased to achieve excellent capacity, and the resistance can be reduced. If the porosity is too low, the electrolyte impregnation property may decrease and lithium precipitation may occur due to the non-impregnation of the electrolyte. If the porosity is too high, the contact between the electrodes may not be good, the resistance may increase, the energy density may decrease, and the effect of improving the capacity may be low.

[0286] The porosity numerical value of the positive electrode active material layer can be achieved by i) the positive electrode active material containing single-particle active material particles, and ii) adding flaky graphite to the positive electrode active material.

[0287] When realizing a high-loading electrode with a relatively high loading amount of the positive electrode active material layer, when using a positive electrode active material in the form of single particles or pseudo-single particles as in an embodiment of the present invention, compared with the conventional positive electrode active material in the form of secondary particles, the particle cracking of the active material during rolling is significantly reduced, and the damage to the positive electrode current collector (Al foil) is reduced. Therefore, it becomes possible to roll at a relatively high linear pressure, and the porosity of the positive electrode active material layer is reduced to the numerical range as described above, and the energy density can be increased.

[0288] Also, when the positive electrode active material layer contains flaky graphite as in an embodiment of the present invention, the flaky graphite provides a sliding effect during rolling and can fill the voids of the positive electrode active material layer. Therefore, the porosity of the positive electrode active material layer can be reduced to the numerical range as described above.

[0289] Also, the loading amount of the positive electrode is 570 mg / 25 cm 2 or more, desirably 600 mg / 25 cm 2 ~800 g / 25 m 2 More desirably, it is 600 mg / 25 cm 2 ~750 mg / 25 cm 2 It can be. Specifically, in the case of a lithium secondary battery according to an embodiment of the present invention, by applying a positive electrode active material and flaky graphite in the form of single particles and / or pseudo-single particles, the rolling characteristics of the electrode are improved. Therefore, the loading amount of the positive electrode can be ensured at a relatively high level, and thereby high-capacity characteristics can be realized.

[0290] In one embodiment of the present invention, the positive electrode active material layer may further contain a conductive material. The conductive material is used to impart conductivity to the electrode, and can be used without particular limitation as long as it has electron conductivity without causing chemical changes inside the battery. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotube; metal 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. Among these, one kind alone or a mixture of two or more kinds can be used. The conductive material may usually be contained in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, more preferably 1 wt% to 10 wt% based on the total weight of the positive electrode active material layer.

[0291] In a specific embodiment of the present invention, the conductive material may include carbon nanotubes.

[0292] In one embodiment of the present invention, the positive electrode active material may include multi-walled carbon nanotubes having a high specific surface area and a small number of layers (wall number) as a conductive material. The multi-walled carbon nanotubes may be contained in an amount of 50 wt% or more, 70 wt% or more, 90 wt% or more, or 99 wt% or more based on 100 wt% of the conductive material. In a specific embodiment of the present invention, the conductive material may be composed only of the multi-walled carbon nanotubes.

[0293] In one example of the present invention, the multi-walled carbon nanotubes have a BET specific surface area of 300 m 2 / g to 500 m 2 / g. To distinguish this from the prior art, it is referred to as "novel CNT".

[0294] Conventionally, generally used carbon nanotubes (conventional CNTs) have a BET specific surface area of 300 m 2It is less than / g. When comparing the scanning electron microscope images and physical properties of the novel CNT (Figure 22) and the conventional CNT (Figure 23) used in the present invention (Figure 24), it is as follows.

[0295] As can be seen from the SEM image, the novel CNT applied to an embodiment of the present invention is of a bundled type and has a multi-wall structure. However, compared with the conventional CNT, it has a higher BET, a smaller number of layers and diameter.

[0296] When using the cathode active material in the form of secondary particles, sufficient electrical conductivity can be realized even when using the conventional CNT at about 0.4 wt% to 0.6 wt%. However, in the case of the cathode active material in the form of single particles or pseudo single particles, the resistance is higher than that of the conventional cathode active material in the form of secondary particles, the contact area with the conductive material is small and the electrical conductivity decreases. Therefore, in order to realize sufficient electrical conductivity by using a conventional CNT with a BET specific surface area of less than 300 m 2 / g, the content of the conductive material must be 0.9 wt% or more.

[0297] Figures 25 to 28 are graphs showing the surface resistance and high-temperature life characteristics according to the ratio of the conductive material when applying single particles or pseudo single particles as the cathode active material.

[0298] From the graph, it can be seen that when applying single particles or pseudo single particles as the cathode active material, it is necessary to increase the amount of the conductive material used compared with the case of applying the conventional cathode active material in the form of secondary particles.

[0299] However, if the content of the carbon nanotube increases to 0.9 wt% or more, aggregation occurs in the cathode slurry and the viscosity increases, thereby reducing the coating property. Therefore, in order to realize a smooth coating property, it is necessary to reduce the solid content in the cathode slurry to lower the viscosity of the cathode slurry. However, when the solid content in the cathode slurry decreases, there is a problem that the active material content decreases and the capacity characteristics deteriorate.

[0300] As a result of repeated research to solve such problems, the inventors of the present invention found that, together with the positive electrode active material which is a single-particle-based active material particle, carbon nanotubes with a BET specific surface area of 300 m 2 / g to 500 m 2 / g are applied, even a relatively small amount of carbon nanotubes can ensure sufficient electrical conductivity. Thus, it was confirmed that even when the solid content of the positive electrode slurry is increased to about 70 wt% to 80 wt%, the slurry viscosity can be kept low.

[0301] Specifically, the carbon nanotubes used in the present invention may be multi-walled carbon nanotubes having a BET specific surface area of 300 m 2 / g to 500 m 2 / g, preferably 300 m 2 / g to 450 m 2 / g. When the BET specific surface area satisfies the above range, sufficient electrical conductivity can be ensured even with a small amount of carbon nanotubes.

[0302] Further, the carbon nanotubes may be multi-walled carbon nanotubes having a layer number (wall number) of 2 to 8, preferably 2 to 6, more preferably 3 to 6.

[0303] Further, the carbon nanotubes may have a diameter of 1 nm to 8 nm, preferably 3 nm to 8 nm, more preferably 3 nm to 6 nm.

[0304] The carbon nanotubes may be contained in an amount of 0.7 wt% or less, preferably 0.3 wt% to 0.7 wt%, more preferably 0.4 wt% to 0.6 wt% based on the total weight of the positive electrode active material layer. When the content of the carbon nanotubes satisfies the above range, sufficient electrical conductivity can be realized and the solid content in the positive electrode slurry can be kept high. Therefore, the content of the positive electrode active material in the positive electrode active material layer can be increased, and excellent capacity characteristics can thereby be realized.

[0305] The table shown in FIG. 29 shows that the BET specific surface area is 300 m 2 / g to 500 m2 When applying carbon nanotubes (new CNTs) with a BET specific surface area of 200 m 2 / g or more and less than 300 m 2 / g (conventional CNTs), the solid content, viscosity, resistance value in the MP coating layer, and resistance value in the MP interface layer of the positive electrode slurry were compared. From the table, it can be confirmed that when applying new CNTs, even when the solid content of the positive electrode slurry is higher than that of conventional CNTs, it shows a lower viscosity and also has excellent electrical conductivity.

[0306] The binder plays a role in improving the adhesion between the positive electrode active material particles and the adhesion force 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, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene monomer (EPDM) rubber, sulfonated EPDM, styrene - butadiene rubber (SBR), fluorine rubber, or various copolymers thereof, etc. One of these alone or a mixture of two or more can be used. The binder can be contained in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, more preferably 1 wt% to 10 wt% based on the total weight of the positive electrode active material layer.

[0307] Another embodiment of the present invention relates to an electrode assembly including the positive electrode and a battery including the same. The electrode assembly includes a negative electrode and a positive electrode, and the positive electrode has the structural features as described above.

[0308] The electrode assembly may be laminated, for example, with a separator interposed between the negative electrode and the positive electrode to form a laminated or laminated / folded structure, or may be wound to form a jelly roll structure. When forming a jelly roll structure, a separator may be further disposed on the outside to prevent contact between the negative electrode and the positive electrode.

[0309] The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector. The negative electrode may have a structure in which a negative electrode active material layer is formed on one or both surfaces of a long sheet-like negative electrode current collector, and the negative electrode active material layer may include a negative electrode active material, a conductive material, and a binder.

[0310] Specifically, the negative electrode can be manufactured by applying a negative electrode slurry, which is prepared 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 surfaces of a long sheet-like negative electrode current collector, removing the solvent of the negative electrode slurry through a drying process, and then rolling. When applying the negative electrode slurry, a negative electrode without a coated area can be manufactured by 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.

[0311] As the negative electrode active material, a compound capable of reversible insertion and deintercalation of lithium can be used. Specific examples 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), SiO y (where 0 < y < 2), Si-C composite, etc.; lithium metal thin film; metal materials capable of alloying with lithium such as Sn, Al, etc. One or a mixture of two or more of these can be used.

[0312] In one embodiment of the present invention, the negative electrode may include a silicon-based negative electrode active material. The silicon-based negative electrode active material may 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), SiO y (where 0 < y < 2), a Si-C composite, or a combination thereof, preferably SiO y (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.

[0313] The silicon-based negative electrode active material may be doped with M b metal, and at this time, the M b metal may be a Group 1 metal element or a Group 2 metal element, specifically, it may be Li, Mg, etc. Specifically, the silicon-based negative electrode active material may be Si doped with M b metal, SiO y (where 0 < y < 2), a Si-C composite, etc. In the case of a metal-doped silicon-based negative electrode active material, although the active material capacity decreases somewhat due to the doping element, it has high efficiency, so a high energy density can be realized.

[0314] FIG. 46 is a graph showing the change in energy density according to the content of the silicon-based negative electrode active material and the presence or absence of doping of the silicon-based negative electrode active material in a battery using a mixture of the silicon-based negative electrode active material and the carbon-based negative electrode active material as the negative electrode active material.

[0315] In FIG. 46, low-efficiency SiO is undoped SiO, and ultra-high-efficiency SiO means Mg / Li-doped SiO. From FIG. 46, it can be confirmed that the energy density improves as the content of the silicon-based negative electrode active material in the total negative electrode active material increases. Also, it can be confirmed that the improvement effect of the energy density is more excellent as the ratio of the doped silicon-based negative electrode active material in the silicon-based negative electrode active material increases.

[0316] The silicon-based negative electrode active material may further include a carbon coating layer on the surface of the particles. At this time, the amount of the carbon coating may be 20 wt% or less, preferably 1 to 20 wt% based on the total weight of the silicon-based negative electrode active material. The carbon coating layer may be formed through methods such as dry coating, wet coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), etc.

[0317] In one embodiment of the present invention, the silicon-based negative electrode active material may have a capacity of 1,000 to 4,000 mAh / g and an initial efficiency of about 60 to 95%.

[0318] In another embodiment of the present invention, the D of the silicon-based negative electrode active material 50 may be 3 μm to 8 μm, and D min ~D max may be included in the range of 0.5 μm to 30 μm.

[0319] The negative electrode may further include a carbon-based negative electrode active material as a negative electrode active material as needed. The carbon-based negative electrode active material may be, for example, artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, etc., but is not limited thereto.

[0320] When using a mixture of a silicon-based negative electrode active material and a carbon-based negative electrode active material as the negative electrode active material, the mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material may be 1:99 to 20:80, preferably 1:99 to 15:85, more preferably 1:99 to 10:90 in weight ratio.

[0321] The negative electrode active material may be included at 80 wt% to 99 wt%, preferably 85 wt% to 99 wt%, more preferably 90 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0322] As needed, the negative electrode active material may further include one or more selected from lithium metal and metal substances capable of alloying with lithium such as Sn and Al.

[0323] As the negative electrode current collector, a negative electrode current collector generally used in the art can be used. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those surface-treated with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used. The negative electrode current collector can usually have a thickness of 3 μm to 500 μm. Similar to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the binding force of the negative electrode active material. For example, the negative electrode current collector can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabrics, etc.

[0324] The conductive material is used to impart conductivity to the negative electrode. As long as it has electron conductivity without causing chemical changes inside the battery, it can be used without particular limitation. Specific examples of the conductive material include graphite such as natural graphite and artificial graphite; carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube; metal powders or metal fibers such as copper, nickel, aluminum, silver; conductive whiskers such as zinc oxide, potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more can be used. The conductive material can usually be contained in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, more preferably 1 wt% to 10 wt% based on the total weight of the negative electrode active material layer.

[0325] The binder plays a role in improving the adhesion between negative electrode active material particles and the adhesion between the negative electrode active material and the negative electrode current collector. Examples of specific binders include polyvinylidene fluoride (PVDF), vinylidene fluoride - hexafluoropropylene copolymer (PVDF - co - HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene - propylene - diene monomer (EPDM) rubber, sulfonated EPDM, styrene - butadiene rubber (SBR), fluorine rubber, or various copolymers thereof, etc. One of these alone or a mixture of two or more thereof can be used. The binder can be contained in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, more preferably 1 wt% to 10 wt% based on the total weight of the negative electrode active material layer.

[0326] The electrode assembly further includes a separator, and the separator is disposed in the electrode assembly in such a manner as to be interposed between the negative electrode and the positive electrode. The separator separates the negative electrode and the positive electrode and provides a migration path for lithium ions, and can be used without particular limitation as long as it is usually used as a separator in a lithium battery.

[0327] Examples of the separator include porous polymer films, such as porous polymer films made from polyolefin - based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof. Also, ordinary porous non - woven fabrics, such as non - woven fabrics made of high - melting - point glass fibers, polyethylene terephthalate fibers, etc., may be used. Further, for ensuring heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer substance may be used.

[0328] Still another embodiment of the present invention relates to a battery including the electrode assembly. In the battery, the electrode assembly and the electrolyte are housed together in a battery case. As the battery case, any suitable one can be selected without particular limitation as long as it is commonly used in the art, such as a pouch type or a metal can type.

[0329] As the electrolyte used in the present invention, various electrolytes that can be used in lithium batteries can be used, for example, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., and the types thereof are not particularly limited.

[0330] Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0331] As the organic solvent, any solvent can be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent 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; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a hydrocarbon group having a linear, branched, or cyclic structure with 2 to 20 carbon atoms and may contain a double bond, aromatic ring, or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among these, carbonate solvents are desirable, and a mixture of a cyclic carbonate having a high ion conductivity and high dielectric constant that can improve the charge and discharge performance of the battery (for example, ethylene carbonate or propylene carbonate) and a linear carbonate compound having a low viscosity (for example, ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more desirable.

[0332] The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium battery. 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 can be within the range of 0.1 to 5.0 M, preferably 0.1 M to 3.0 M. If the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, thus showing excellent electrolyte performance and enabling effective movement of lithium ions.

[0333] In addition to the above-described electrolyte components, the electrolyte may further contain additives for the purpose of improving battery life characteristics, suppressing battery capacity reduction, improving the discharge capacity of the battery, etc. For example, as the additive, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, etc. can be used alone or in combination, but is not limited thereto. The additive can be contained in an amount of 0.1 wt% to 10 wt%, preferably 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0334] In still another embodiment of the present invention, the positive electrode may include a loading reduction portion where the loading amount of the positive electrode active material is less than that in the adjacent region. When the positive electrode has such a structure, the section of the positive electrode active material portion can be increased without fear of lithium precipitation. Thereby, the energy density of the electrode assembly can be improved.

[0335] In recent years, in order to achieve a high energy density and reduce costs, development has been progressing in the direction of increasing the size of batteries. As the energy increases according to the size of the battery, the resistance per battery must decrease. To reduce the resistance, instead of attaching an electrode tab to the electrode, a method of utilizing the current collector of the electrode as the electrode tab can be used. At this time, due to the characteristics of the electrode manufacturing process of applying the electrode slurry onto the electrode current collector, a portion where the loading amount decreases occurs at the boundary between the negative electrode active material portion coated with the negative electrode slurry and the negative electrode current collector. Considering the N / P ratio, there is a risk that metallic lithium may precipitate on the positive electrode active material portion facing the portion where the loading amount decreases. Here, the N / P ratio is a value obtained by dividing the capacity of the negative electrode calculated based on the area and capacity per mass of the negative electrode by the capacity of the positive electrode obtained based on the area and capacity per mass of the positive electrode, and generally has a value of 1 or more. That is, the capacity of the negative electrode is manufactured to be larger. For reference, if the N / P ratio does not become 1, metallic lithium is likely to precipitate during charge and discharge, which causes the safety of the battery to rapidly deteriorate during high-rate charge and discharge. In other words, the N / P ratio has a great influence on the safety and capacity of the battery. Thus, due to the risk of precipitation of metallic lithium, the positive electrode active material portion cannot be positioned in the positive electrode portion facing the portion where the loading amount of the negative electrode decreases. This causes the energy density of the battery not to be increased. Therefore, the present invention increases the section of the positive electrode active material portion to improve the energy density.

[0336] FIG. 34 is a diagram showing an electrode assembly according to an embodiment of the present invention, and FIG. 35 is a cross-sectional view taken along line A-A' of FIG. 34.

[0337] Referring to FIGS. 34 and 35, an electrode assembly 300 according to an embodiment of the present invention includes a negative electrode 400, a positive electrode 500, and a separator 600. The separator 600 is positioned between the negative electrode 400 and the positive electrode 500. The negative electrode 400, the positive electrode 500, and the separator 600 are wound together to form a jelly roll structure 300S. Here, the jelly roll structure 300S refers to a structure formed by winding the negative electrode 400, the positive electrode 500, and the separator 600. Further, when forming the jelly roll structure 300S, it is desirable to further dispose the separator 600 on the outside to prevent the negative electrode 400 and the positive electrode 500 from contacting each other.

[0338] The negative electrode 400 includes a negative electrode current collector 410 and a negative electrode active material portion 420 formed by applying a negative electrode active material on the negative electrode current collector 410. In particular, as shown in the figure, the negative electrode active material can be applied to both sides of the negative electrode current collector 410 to form the negative electrode active material portion 420. Further, a negative electrode blank portion 430 where the negative electrode active material is not applied extends in the first direction d1 in the negative electrode current collector 410. The negative electrode blank portion 430 extends along one end of the wound negative electrode 400. Further, the negative electrode blank portion 430 extends longer than the separator 600 in the first direction d1. Thereby, the negative electrode blank portion 430 can be exposed at one end of the jelly roll structure 300S in the first direction.

[0339] The positive electrode 500 includes a positive electrode current collector 510 and a positive electrode active material portion 520 formed by applying a positive electrode active material on the positive electrode current collector 510. In particular, as shown in the figure, the positive electrode active material can be applied to both sides of the positive electrode current collector 510 to form the positive electrode active material portion 520. Further, a positive electrode blank portion 530 where the positive electrode active material is not applied extends in the second direction d2 in the positive electrode current collector 510. The positive electrode blank portion 530 extends along one end of the wound positive electrode 500. Further, the positive electrode blank portion 530 extends longer than the separator 600 in the second direction d2. Thereby, the positive electrode blank portion 530 can be exposed at one end of the jelly roll structure 300S in the second direction.

[0340] Here, the first direction d1 and the second direction d2 are opposite directions. Also, the first direction d1 and the second direction d2 can be directions parallel to the height direction of the jelly roll structure 300S.

[0341] The electrode assembly 300 according to the present embodiment does not have a form in which a separate electrode tab is attached, but rather utilizes the negative electrode non-coated portion 430 of the negative electrode current collector 410 and the positive electrode non-coated portion 530 of the positive electrode current collector 510 themselves as electrode tabs for resistance reduction.

[0342] Although not shown, the negative electrode non-coated portion 430 and / or the positive electrode non-coated portion 530 may substantially have the same structure as the non-coated portion of the electrode described with reference to FIGS. 14 to 20.

[0343] In one embodiment, the positive electrode active material portion 520 includes a loading reduction portion 500D where the loading amount of the positive electrode active material is less than that in the adjacent region, and the loading reduction portion 500D is located at one end of the positive electrode 500 in the first direction d1. More specifically, in the first direction d1, the loading amount of the positive electrode active material may gradually decrease.

[0344] Here, the loading amount means the coating amount of the active material per unit area. In a portion where the loading amount is large, a large amount of negative electrode active material or positive electrode active material is coated per unit area, and the thickness of the negative electrode active material portion or the positive electrode active material portion can be relatively thick. In a portion where the loading amount is small, a small amount of negative electrode active material or positive electrode active material is coated per unit area, and the thickness of the negative electrode active material portion or the positive electrode active material portion can be relatively thin.

[0345] A slurry containing an active material is applied to form the active material portion, and in such a process, a boundary portion where the loading amount gradually decreases can be formed between the non-coated portion and the active material portion.

[0346] Specifically, the negative electrode active material portion 420 may include a negative electrode boundary portion 420B that forms a boundary between the negative electrode active material portion 420 and the negative electrode non-coated portion 430. The loading amount of the negative electrode boundary portion 420B may gradually decrease in the direction in which the negative electrode non-coated portion 430 is located.

[0347] Similarly, the positive electrode active material portion 520 may include a positive electrode boundary portion 520B that forms a boundary between the positive electrode active material portion 520 and the positive electrode non-coated portion 530. The loading amount of the positive electrode boundary portion 520B may gradually decrease in the direction in which the positive electrode non-coated portion 530 is located.

[0348] The negative electrode boundary portion 420B and the positive electrode boundary portion 520B in which the loading amount gradually decreases in this way occur naturally in the process of applying the slurry containing the active material to the negative electrode current collector 410 and the positive electrode current collector 510.

[0349] At this time, based on the direction perpendicular to the second direction d2, in the region corresponding to the positive electrode boundary portion 520B, the amount of the positive electrode active material is less than the amount of the negative electrode active material. As a result, since the N / P ratio becomes a value greater than 1, problems such as precipitation of metallic lithium do not occur.

[0350] However, there is a problem in the region corresponding to the negative electrode boundary portion 420B. Based on the direction perpendicular to the first direction d1, in the region corresponding to the negative electrode boundary portion 420B, the amount of the negative electrode active material is less than the amount of the positive electrode active material. As a result, since the N / P ratio becomes a value less than 1, there is a risk that problems such as precipitation of metallic lithium may occur.

[0351] Therefore, in the present embodiment, a loading reduction portion 500D is provided in the positive electrode 500, and the negative electrode active material portion 420 is positioned at a portion corresponding to the loading reduction portion 500D based on the direction perpendicular to the first direction d1. More specifically, based on the direction perpendicular to the first direction d1, the negative electrode boundary portion 420B may be located at a portion corresponding to the loading reduction portion 500D.

[0352] By providing a loading reduction portion 500D where the loading amount of the positive electrode active material is less than that of the adjacent region at a position corresponding to the negative electrode boundary portion 420B where the loading amount gradually decreases, it is possible to increase the section coated with the positive electrode active material without worrying about lithium precipitation. In particular, the loading reduction portion 500D may have a form in which the loading amount of the positive electrode active material gradually decreases in the first direction d1 so as to correspond to the shape of the negative electrode boundary portion 420B where the loading amount gradually decreases toward the negative electrode non-coated portion 430. Therefore, the N / P ratio with respect to the negative electrode 400 and the positive electrode 500 in the region where the negative electrode boundary portion 420B is formed can be maintained high, and lithium precipitation can be prevented.

[0353] Hereinafter, a method for manufacturing an electrode assembly according to an embodiment of the present invention will be described in detail with reference to FIGS. 36 to 41.

[0354] FIGS. 36 and 37 are views showing the process of manufacturing a negative electrode according to an embodiment of the present invention. Specifically, FIG. 36 is a top view of the negative electrode sheet, and FIG. 37 is a front view of the negative electrode sheet of FIG. 36.

[0355] Referring to FIGS. 36 and 37, a method for manufacturing an electrode assembly according to an embodiment of the present invention includes a step of manufacturing a negative electrode sheet 400S such that a negative electrode active material portion 420 coated with a negative electrode active material and a negative electrode non-coated portion 430 not coated with a negative electrode active material are alternately positioned on a negative electrode current collector 410.

[0356] Specifically, the negative electrode active material portion 420 can be formed by applying the negative electrode active material so as to extend in the third direction d3. Further, by separating the coating regions along a fourth direction d4 perpendicular to the third direction d3, the plurality of negative electrode active material portions 420 can be separated and positioned along the fourth direction d4. That is, the coating process can be performed so that the negative electrode non-coated portion 430 is positioned between the plurality of negative electrode active material portions 420.

[0357] Here, the third direction d3 and the fourth direction d4 are directions for explanation with reference to the negative electrode sheet 400S, and are directions unrelated to the first direction d1 and the second direction d2 in the jelly roll structure 300S described above.

[0358] Thereafter, a step of manufacturing the negative electrode 400 by slitting the negative electrode blank portion 430 and the negative electrode active material portion 420 may be included. FIG. 38 is a perspective view showing a negative electrode according to an embodiment of the present invention.

[0359] Referring to FIGS. 36 to 38, slitting can be performed in a direction parallel to the third direction d3 with respect to each of the negative electrode blank portion 430 and the negative electrode active material portion 420, as shown by the dashed-dotted line in FIGS. 36 and 37. Thereby, a plurality of negative electrodes 400 as shown in FIG. 38 can be manufactured from the negative electrode sheet 400S. That is, the negative electrode 400 in FIG. 38 corresponds to one of the plurality of negative electrodes manufactured by slitting the negative electrode sheet 400S in FIGS. 36 and 37. By slitting the negative electrode blank portion 430 and the negative electrode active material portion 420 in the negative electrode sheet 400S, respectively, a negative electrode 400 in which the negative electrode blank portion 430 extends to one side can be manufactured.

[0360] When forming the negative electrode active material portion 420, a slurry containing the negative electrode active material is applied onto the negative electrode current collector 410. In such a slurry application process, a negative electrode boundary portion 420B in which the loading amount gradually decreases in the direction in which the negative electrode blank portion 430 is located may be formed at the boundary between the negative electrode active material portion 420 and the negative electrode blank portion 430.

[0361] FIGS. 39 and 40 are diagrams showing a process of manufacturing a positive electrode according to an embodiment of the present invention. Specifically, FIG. 39 is a top view of the positive electrode sheet, and FIG. 40 is a front view of the positive electrode sheet in FIG. 39.

[0362] Referring to FIGS. 39 and 40, a method for manufacturing an electrode assembly according to an embodiment of the present invention includes a step of manufacturing a positive electrode sheet 500S such that a positive electrode active material portion 520 coated with a positive electrode active material and a positive electrode non-coated portion 530 not coated with a positive electrode active material are alternately positioned on a positive electrode current collector 510.

[0363] Specifically, the positive electrode active material may be applied so as to extend in the third direction d3 to form the positive electrode active material portion 520. Further, by adjusting the application interval along a fourth direction d4 perpendicular to the third direction d3, a plurality of positive electrode active material portions 520 can be separated and positioned. That is, the application process can be performed such that the positive electrode non-coated portion 530 is positioned between the plurality of positive electrode active material portions 520.

[0364] Here, the third direction d3 and the fourth direction d4 are directions for explanation with reference to the positive electrode sheet 500S, and are directions not related to the first direction d1 and the second direction d2 in the jelly roll structure 300S described above.

[0365] Thereafter, it may include a step of manufacturing the positive electrode 500 by slitting the positive electrode non-coated portion 530 and the positive electrode active material portion 520. FIG. 41 is a perspective view showing the positive electrode 500 according to an embodiment of the present invention.

[0366] Referring to FIGS. 39 to 41, slitting can be performed in a direction parallel to the third direction d3 with respect to each of the positive electrode non-coated portion 530 and the positive electrode active material portion 520 as shown by the dashed-dotted line portions in FIGS. 39 and 40. As a result, a plurality of positive electrodes 500 as shown in FIG. 41 can be manufactured from the positive electrode sheet 500S. That is, the positive electrode 500 in FIG. 41 corresponds to one of the plurality of positive electrodes manufactured by slitting the positive electrode sheet 500S in FIGS. 39 and 40. By slitting the positive electrode non-coated portion 530 and the positive electrode active material portion 520 in the positive electrode sheet 500S, a positive electrode 500 having the positive electrode non-coated portion 530 extending on one side can be manufactured.

[0367] When forming the positive electrode active material portion 520, a slurry containing the positive electrode active material is applied onto the positive electrode current collector 510. In such a slurry application process, a positive electrode boundary portion 520B in which the loading amount gradually decreases in the direction in which the positive electrode non-coated portion 530 is located may be formed at the boundary between the positive electrode active material portion 520 and the positive electrode non-coated portion 530.

[0368] Referring to FIGS. 34, 38, and 41 together, the step of winding the manufactured negative electrode 400 and positive electrode 500 together with the separator 600 to form the jelly roll structure 300S may be subsequently performed. At this time, in the jelly roll structure 300S, the negative electrode non-coated portion 430 may extend longer than the separator 600 in the first direction d1, and the positive electrode non-coated portion 530 may extend longer than the separator 600 in the second direction d2 opposite to the first direction d1.

[0369] Referring further to FIGS. 39 to 41, in the method for manufacturing an electrode assembly according to an embodiment of the present invention, the positive electrode sheet 500S includes a loading reduction region 500DA where the loading amount of the positive electrode active material is less than that in the adjacent region. There is no particular limitation on the method for forming the loading reduction region 500DA, and for example, it may be formed by adjusting the degree of slurry application.

[0370] In the step of manufacturing the positive electrode 500, the loading reduction region 500DA is slit from the positive electrode active material portion 520. The slit loading reduction region 500DA forms a loading reduction portion 500D where the loading amount of the positive electrode active material is less than that in the adjacent region in the jelly roll structure 300S shown in FIGS. 34 and 35.

[0371] Specifically, a loading reduction region 500DA where the loading amount of the positive electrode active material is less than that in the adjacent region is formed in the positive electrode active material portion 520 formed on the positive electrode sheet 500S. As shown in FIG. 40, the loading reduction region 500DA can be formed at the center of the positive electrode active material portion 520. On the other hand, the loading reduction region 500DA can be configured such that the loading amount of the positive electrode active material gradually decreases toward the central portion 500C of the loading reduction region 500DA. In the step of manufacturing the positive electrode 500, the loading reduction portion 500D according to the present embodiment can be formed by slitting the central portion 500C of the loading reduction region 500DA.

[0372] That is, the loading reduction region 500DA can be formed by applying a slurry containing a positive electrode active material, and a plurality of positive electrodes 500 in which the loading reduction portion 500D is formed can be manufactured by slitting the central portion 500C of the loading reduction region 500DA.

[0373] Referring to FIG. 41, a loading reduction portion 500D is provided at one end of the manufactured positive electrode 500, and a positive electrode blank portion 530 can be provided at the other end of the positive electrode 500 facing the one end.

[0374] Referring to FIGS. 34 and 35, when such a positive electrode 500 is wound to form the jelly roll structure 300S, the loading reduction portion 500D is located at one end of the positive electrode 500 in the first direction d1, and the positive electrode blank portion 530 can be located at one end of the positive electrode 500 in the second direction d2.

[0375] Further, by slitting the central portion 500C of the loading reduction region 500DA, the loading amount of the positive electrode active material in the loading reduction portion 500D can gradually decrease toward the first direction d1.

[0376] Further, in the jelly roll structure 300S, the negative electrode active material portion 420 may be located at a portion corresponding to the loading reduction portion 500D with reference to the direction perpendicular to the first direction d1. More specifically, in the jelly roll structure 300S, the negative electrode boundary portion 420B may be located at a portion corresponding to the loading reduction portion 500D with reference to the direction perpendicular to the first direction d1.

[0377] The corresponding positional relationship between the loading reduction portion 500D and the negative electrode boundary portion 420B is the same as the above-described explanation, and thus is omitted.

[0378] Hereinafter, an electrode assembly according to a comparative form of the present invention will be described with reference to FIGS. 42 to 45, and advantages of the electrode assembly according to an embodiment of the present invention over the electrode assembly according to the comparative form will be described.

[0379] FIG. 42 is a diagram showing an electrode assembly according to a comparative form of the present invention, and FIG. 43 is a cross-sectional view taken along line B-B' of FIG. 42.

[0380] Referring to FIGS. 42 and 43, an electrode assembly 600 according to a comparative form of the present invention includes a negative electrode 700, a positive electrode 800, and a separator 900, and the negative electrode 700, the positive electrode 800, and the separator 900 are wound to form a jelly roll structure 600S.

[0381] The negative electrode 700 may include a negative electrode current collector 710, a negative electrode active material portion 720, and a negative electrode blank portion 730. Further, the negative electrode blank portion 730 may extend in the first direction d1, and the negative electrode active material portion 720 may include a negative electrode boundary portion 720B in which the loading amount gradually decreases while forming a boundary between the negative electrode active material portion 720 and the negative electrode blank portion 730.

[0382] FIG. 44 is a diagram showing a process of manufacturing the negative electrode 700 according to a comparative form of the present invention.

[0383] Referring to FIG. 44, after the negative electrode sheet 700S is manufactured such that the negative electrode active material portion 720 and the negative electrode non-coated portion 730 are alternately positioned along the fourth direction d4, the negative electrode non-coated portion 730 and the negative electrode active material portion 720 may be slit to manufacture a plurality of negative electrodes 700.

[0384] On the other hand, referring further to FIGS. 42 and 43, the positive electrode 800 may include a positive electrode current collector 810, a positive electrode active material portion 820, and a positive electrode non-coated portion 830. Further, the positive electrode non-coated portion 830 may extend in the second direction d2 facing the first direction d1, and the positive electrode active material portion 820 may include a positive electrode boundary portion 820B where the loading amount gradually decreases while forming a boundary between the positive electrode active material portion 820 and the positive electrode non-coated portion 830.

[0385] FIG. 45 is a diagram showing a process of manufacturing the positive electrode 800 according to a comparative form of the present invention.

[0386] Referring to FIG. 45, after the positive electrode sheet 800S is manufactured such that the positive electrode active material portion 820 and the positive electrode non-coated portion 830 are alternately positioned along the fourth direction d4, the positive electrode non-coated portion 830 and the positive electrode active material portion 820 may be slit to manufacture a plurality of positive electrodes 800.

[0387] Thereafter, the manufactured negative electrode 700 and positive electrode 800 may be wound together with the separator 900 to manufacture an electrode assembly 600 according to a comparative form of the present invention.

[0388] That is, the electrode assembly 600 according to the comparative form of the present invention may have a structure similar to that of the electrode assembly 300 according to the embodiment of the present invention, except for the loading reduction portion 500D (refer to FIG. 35).

[0389] Referring to FIGS. 42 and 43, in the case of the electrode assembly 600 according to the comparative form, with respect to the direction perpendicular to the first direction d1, the positive electrode active material portion 820 cannot be located at the portion corresponding to the negative electrode boundary portion 720B. If the positive electrode active material portion 820 extends to the portion corresponding to the negative electrode boundary portion 720B, the corresponding portion will have a low N / P ratio, and metallic lithium is likely to precipitate. Therefore, in order to prevent lithium precipitation, the length of the positive electrode active material portion 820 has to be limited. That is, the positive electrode active material portion 820 can be formed only in the illustrated B1 region, the positive electrode active material portion 820 cannot be formed in the B2 region, and as a result, the length of the positive electrode active material portion 820 is reduced by the negative electrode boundary portion 720B.

[0390] On the other hand, referring to FIGS. 34 and 35, in the case of the electrode assembly 300 according to the embodiment of the present invention, with respect to the direction perpendicular to the first direction d1, the positive electrode active material portion 520, particularly the loading reduction portion 500D, can be located at the portion corresponding to the negative electrode boundary portion 420B. Since the loading reduction portion 500D where the loading amount of the positive electrode active material is less than that of the adjacent region is provided at the position corresponding to the negative electrode boundary portion 420B, the N / P ratio at the corresponding portion can be maintained high, and precipitation of lithium can be prevented. Thereby, the positive electrode active material portion 520 can be formed over the A1 region, and the A2 region where the positive electrode active material portion 520 cannot be formed can be reduced. As an example, the width of the positive electrode 500 in the height direction can be increased to 98% or more with respect to the width of the negative electrode 400 in the height direction.

[0391] Comparing the A1 region in FIGS. 34 and 35 with the B1 region in FIGS. 42 and 43, the electrode assembly 300 according to the present embodiment can increase the length of the positive electrode active material portion only by the loading reduction portion 500D. Therefore, a higher energy density can be realized in a limited space as compared with the electrode assembly 600 according to the comparative form.

[0392] Still another embodiment of the present invention relates to a cylindrical battery including a jelly roll type electrode assembly having a structure in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are wound in one direction, a cylindrical battery housing in which the electrode assembly is housed, and a battery cap which is a sealing body disposed on the upper portion of the battery housing to seal the battery housing. Here, the positive electrode is according to an embodiment of the present invention, and contains single particle active material particles having an average particle diameter D 50 of 5 μm or less as a positive electrode active material. The cylindrical battery may further include an electrolytic solution, and for the electrolytic solution, reference may be made to the above description.

[0393] The electrode assembly may have a structure such as a laminated type, a laminated / folded type, or a jelly roll type as described above. In a specific embodiment of the present invention, the electrode assembly may be such that the positive electrode has a loading reduction portion as described above.

[0394] In the case of a conventional cylindrical battery, there is a problem that current is concentrated on a strip-shaped electrode tab, resulting in a large resistance, generation of a large amount of heat, and poor current collection efficiency.

[0395] In recent years, with the development of technologies related to electric vehicles, there has been an increasing demand for high-capacity batteries, and thus the development of large-sized cylindrical batteries with a large volume has been required. In the case of a small-sized cylindrical battery that has generally been used conventionally, that is, a cylindrical battery having a form factor of 1865 or 2170, since the capacity is small, resistance and heat generation do not seriously affect battery performance. However, if the specifications of a conventional small-sized cylindrical battery are directly applied to a large-sized cylindrical battery, there may be a serious problem with battery safety.

[0396] As the battery size increases, the amount of heat and gas generated inside the battery also increases accordingly. However, such heat and gas can cause the temperature and pressure inside the battery to rise, which may lead to the battery catching fire or exploding. To prevent this, the heat and gas inside the battery must be properly discharged to the outside. For this purpose, the cross-sectional area of the battery, which serves as a heat discharge path to the outside of the battery, needs to increase in accordance with the increase in volume. However, usually, the increase in the cross-sectional area does not keep up with the increase in volume. Therefore, as the battery becomes larger, the amount of heat generated inside the battery increases, resulting in problems such as an increased risk of explosion and a decrease in output. In addition, when rapid charging is performed at a high voltage, there is also a risk that the battery may catch fire while generating a large amount of heat around the electrode tab in a short time. Therefore, the present invention proposes a cylindrical battery that has a large volume to achieve a high capacity while having high safety.

[0397] In addition, since the high-loading electrode to which the positive electrode active material in the form of single particles or pseudo-single particles is applied is applied to the cylindrical battery, the initial resistance characteristics and charge-discharge efficiency of the cylindrical battery can be improved.

[0398] The cylindrical battery according to an embodiment of the present invention applies a positive electrode active material in the form of single particles or pseudo-single particles, thereby significantly reducing the amount of gas generation compared to the conventional case. As a result, excellent safety can be achieved even in a large cylindrical battery with a foam factor ratio of 0.4 or more.

[0399] The cylindrical battery according to an embodiment of the present invention is preferably a tabless structure battery that does not include an electrode tab, but is not limited thereto.

[0400] The tabless structure battery may, for example, include a plain portion where the positive electrode and the negative electrode do not have an active material layer formed thereon, a positive electrode plain portion and a negative electrode plain portion are respectively located at the upper end and the lower end of the electrode assembly, a current collector plate is coupled to the positive electrode plain portion and the negative electrode plain portion, and the current collector plate is connected to an electrode terminal.

[0401] When the cylindrical battery is formed in the tabless structure as described above, compared with the conventional battery provided with an electrode tab, current concentration is reduced, so that heat generation inside the battery can be effectively reduced, and thereby the thermal stability of the battery can be improved.

[0402] Hereinafter, the present invention will be described in more detail with specific examples.

[0403] <Example 1> Average particle diameter D 50 has a unimodal particle size distribution of 3 μm and is in the form of single particles, and the positive electrode active material Li[Ni 0.9 Co 0.06 Mn 0.03 Al 0.01 O2, carbon nanotubes, and a PVDF binder were mixed in N-methylpyrrolidone at a weight ratio of 97.8:0.6:1.6 to produce a positive electrode slurry. After applying the positive electrode slurry to one surface of an aluminum current collector sheet, it was dried at 120 ° C. and then rolled to produce a positive electrode.

[0404] A negative electrode active material (a mixture of graphite:SiO = 95:5 (weight ratio)), a conductive material (Super C), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed in water at a weight ratio of 96:2:1.5:0.5 to produce a negative electrode slurry. 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.

[0405] After a separator was interposed between the produced positive electrode and negative electrode and laminated in the order of separator / positive electrode / separator / negative electrode, it was wound up to produce a jelly roll type electrode assembly. After inserting the electrode assembly produced as described above into a cylindrical battery can, an electrolytic solution was injected to produce a 4680 cell.

[0406] <Comparative Example 1> As the positive electrode active material, the large particle size average particle diameter D 50 is 9 μm, and the small particle size average particle diameter D 50 is 4 μm, has a bimodal particle size distribution, and is in the form of secondary particles, Li[Ni 0.9Co 0.05 Mn 0.04 Al 0.01 A 4680 cell was manufactured in the same manner as in Example 1, except that O2 was used.

[0407] <Experimental Example 1> A hot box test was performed on the 4680 cells manufactured according to Example 1 and Comparative Example 1.

[0408] Specifically, the 4680 cells manufactured according to Example 1 and Comparative Example 1 were each placed in a hot box chamber at room temperature, heated to 130°C at a heating rate of 5°C / min, and then maintained for 30 minutes for a hot box evaluation, and the temperature change of the battery over time was measured. For accurate evaluation, the cells of Example 1 were subjected to two hot box evaluations. The measurement results are shown in FIGS. 31a and 31b.

[0409] FIG. 31a is a graph showing the results of the hot box test for the 4680 cells manufactured according to Example 1, and FIG. 31b is a graph showing the results of the hot box test for the 4680 cells manufactured according to Comparative Example 1.

[0410] From FIGS. 31a and 31b, it can be confirmed that in the case of the lithium secondary battery of Example 1 using the single-particle form cathode active material, the voltage and temperature of the battery were stably maintained until 65 minutes elapsed, while the battery temperature of the lithium secondary battery of Comparative Example 1 increased rapidly after 35 minutes.

[0411] <Example 2-1> Having a unimodal particle size distribution and D min = 1.78 μm, D 50 = 4.23 μm, D max = 13.1 μm, and a cathode active material (composition: Li[Ni 0.9 Co 0.06 Mn 0.03 Al 0.01 O2) in which single particles and pseudo single particles are mixed was prepared. FIG. 30a shows the SEM photograph of the cathode active material used in Example 2-1.

[0412] The positive electrode active material, carbon nanotubes, and PVDF binder were mixed in N-methylpyrrolidone at a weight ratio of 97.8:0.6:1.6 to produce a positive electrode slurry. After applying the positive electrode slurry to one side of an aluminum current collector sheet, it was dried at 120°C and then rolled to produce a positive electrode.

[0413] The negative electrode active material (graphite:SiO = 95:5 (weight ratio) mixture), conductive material (Super C), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed in water at a weight ratio of 96:2:1.5:0.5 to produce a negative electrode slurry. After applying the negative electrode slurry to one side of a copper current collector sheet, it was dried at 150°C and then rolled to produce a negative electrode.

[0414] A separator was interposed between the produced positive electrode and negative electrode, and they were laminated in the order of separator / positive electrode / separator / negative electrode, and then wound up to produce a jelly roll type electrode assembly. After inserting the electrode assembly produced as described above into a battery can, an electrolytic solution was injected to produce a 4680 cell.

[0415] <Example 2-2> As the positive electrode active material, a positive electrode active material having a unimodal particle size distribution with D min = 1.38 μm, D 50 = 4.69 μm, D max = 18.5 μm, and a mixture of single particles and pseudo single particles (composition: Li[Ni 0.9 Co 0.06 Mn 0.03 Al 0.01 O2) was used, and a 4680 cell was produced in the same manner as in Example 2-1. Fig. 30b shows an SEM photograph of the positive electrode active material used in Example 2-2.

[0416] <Comparative Example 2-1> A bimodal particle size distribution with a large particle size average particle size D 50 of 9 μm and a small particle size average particle size D 50 of 4 μm, and a positive electrode active material in the form of secondary particles (composition: Li[Ni 0.9Co 0.05 Mn 0.04 Al 0.01 4680 cells were manufactured in the same manner as in Example 2-1, except that [[ID=]]]O2) was used.

[0417] <Comparative Example 2-2> Having a unimodal particle size distribution and D min = 0.892 μm, D 50 = 3.02 μm, D max = 11 μm, and a positive electrode active material in which single particles and pseudo single particles are mixed (composition: Li[Ni 0.9 Co 0.06 Mn 0.03 Al 0.01 O2) was used.

[0418] Fig. 30c shows the SEM photograph of the positive electrode active material used in Comparative Example 2-2.

[0419] <Experimental Example 2-1> Hot box tests were performed on the 4680 cells manufactured according to Example 2-1, 2-2 and Comparative Examples 2-1, 2-2.

[0420] Specifically, the 4680 cells manufactured according to Example 2-1 and Comparative Example 2-1 were respectively placed in a hot box chamber at room temperature, heated to 130 °C at a heating rate of 5 °C / min, maintained for 30 minutes, and then the temperature change of the battery was measured. When thermal runaway and ignition did not occur during the test, it was indicated as pass, and when thermal runaway and / or ignition occurred, it was indicated as fail. Also, for the cells of Example 2-1 and 2-2, the test was performed more than twice for the accuracy of the test.

[0421] The measurement results are shown in Table 1 below, Figure 31c, and Figure 31d. Figure 31c is a graph showing the results of a hot box test on Sample 1 of Example 2-1 and the 4680 cells manufactured by Comparative Example 2-1, and Figure 31d is a graph showing the results of a hot box test on Samples 2 and 3 of Example 2-1, Samples 1 and 2 of Example 2-2, and the 4680 cells manufactured by Comparative Example 2-2.

[0422]

Table 1

[0423] Referring to Table 1, Figure 31c, and Figure 31d, for the 4680 cells of Example 2-1 to which a positive electrode active material in the form of single particles / suspected single particles with D min of 1.0 μm or more was applied, the voltage and temperature of the battery were stably maintained until 65 minutes had elapsed. On the other hand, for Comparative Example 2-1 in which secondary particles were applied as the positive electrode active material and Comparative Example 2-2 in which a positive electrode active material in the form of single particles / suspected single particles with D min of less than 1.0 μm was applied, it was confirmed that the battery temperature increased rapidly.

[0424] <Experimental Example 2-2> For the positive electrodes manufactured in Example 2-1 and Comparative Example 2-1, in order to confirm the degree of cracking of the positive electrode active material particles after rolling, the positive electrode was cut with an ion milling apparatus and then the cross-section was photographed with an SEM. Figure 32a shows a cross-sectional SEM photograph of the positive electrode manufactured in Example 2-1, and Figure 32b shows a cross-sectional SEM photograph of the positive electrode manufactured in Comparative Example 2-1.

[0425] From Figure 32a and Figure 32b, for the positive electrode of Example 2-1, there is almost no cracking of the positive electrode active material particles even after rolling, while for the positive electrode of Comparative Example 2-2 using secondary particles, a large number of cracks in the positive electrode active material particles are observed after rolling.

[0426] <Example 3-1> Having a unimodal particle size distribution and D min = 1.78 μm, D 50 = 4.23 μm, D max= 13.1 μm, and a positive electrode active material powder (composition: Li[Ni 0.9 Co 0.06 Mn 0.03 Al 0.01 O2), flaky graphite (SFG6L), a conductive material (multi-walled carbon nanotubes), and a PVDF binder were mixed in N-methylpyrrolidone at a weight ratio of 96.3:1.5:0.4:1.8 to produce a positive electrode slurry. The positive electrode slurry was applied to one side of an aluminum current collector sheet, dried, and rolled at a linear pressure of 3.0 ton / cm to produce a positive electrode. The porosity of the positive electrode active material layer of the produced positive electrode was measured. The porosity was 17.5%.

[0427] <Example 3-2> A positive electrode was produced in the same manner as in Example 3-1 except that the positive electrode active material, flaky graphite, the conductive material, and the binder were mixed at a weight ratio of 97.2:0.6:0.4:1.8, and the porosity of the positive electrode active material layer was measured. The porosity was 19%.

[0428] <Example 3-3> A positive electrode was produced in the same manner as in Example 3-1 except that the positive electrode active material, flaky graphite, the conductive material, and the binder were mixed at a weight ratio of 97.4:0.4:0.4:1.8, and the porosity of the positive electrode active material layer was measured. The porosity was 20%.

[0429] <Example 3-4> A positive electrode was produced in the same manner as in Example 3-1 except that the positive electrode active material, flaky graphite, the conductive material, and the binder were mixed at a weight ratio of 97.6:0.2:0.4:1.8, and the porosity of the positive electrode active material layer was measured. The porosity was 21%.

[0430] <Comparative Example 3-1> A positive electrode was produced in the same manner as in Example 3-1 except that no flaky graphite was added, and the positive electrode active material, the conductive material, and the binder were mixed in N-methylpyrrolidone at a weight ratio of 97.8:0.4:1.8 to produce a positive electrode slurry. The porosity of the positive electrode active material layer was measured. The porosity was 24%.

[0431] <Comparative Example 3-2> A positive electrode slurry was prepared by mixing a positive electrode active material, a conductive material, and a binder in a weight ratio of 97.8:0.4:1.8 in N-methylpyrrolidone without adding flaky graphite, and a positive electrode was produced in the same manner as in Example 3-1 except that it was rolled at a linear pressure of 2.0 ton / cm, and the porosity of the positive electrode active material layer was measured. The porosity was 30%.

[0432] <Experimental Example 3-1. Measurement of Charge and Discharge Capacity and Charge and Discharge Efficiency> Coin-type half cells containing the positive electrodes according to Examples 3-1 to 3-4, Comparative Examples 3-1 and 3-2 were manufactured, charged to 4.25 V under a 0.2C current condition, and then discharged to 2.5 V under a 0.2C current condition, and the charge capacity (mAh / g) and discharge capacity (mAh / g) of each coin-type half cell were measured. The measurement results are shown in Table 2 below.

[0433]

Table 2

[0434] From Table 2, it can be confirmed that in the cases of Examples 3-1 to 3-4 using positive electrodes to which flaky graphite was added, they showed a lower porosity and excellent capacity characteristics compared to Comparative Examples 3-1 and 3-2.

[0435] <Experimental Example 3-2. Confirmation of Resistance Characteristics> While charging the coin-type half cells containing the positive electrodes according to Example 3-3, Comparative Example 3-1, and Comparative Example 3-2 to 4.2 V, the resistance characteristics according to the SOC were measured. The results of the experiment are shown in Fig. 33a.

[0436] Referring to Fig. 33a, it can be confirmed that based on SOC10%, the resistance value of Example 3-3 in which flaky graphite was added to the positive electrode active material layer is lower than that of Comparative Example 3-1 and Comparative Example 3-2 that do not contain flaky graphite. This indicates that when flaky graphite is added to the positive electrode active material layer, it has the effect of improving the resistance characteristics at low SOC.

[0437] <Experimental Example 3-3. Measurement of High-Temperature Life Characteristics and Resistance Increase Rate> After a separator was interposed between the positive electrode and the negative electrode according to Example 3-1, Example 3-3, and Comparative Example 3-1, and they were laminated in the order of separator / positive electrode / separator / negative electrode, and then wound up to produce a jelly roll type electrode assembly. After inserting the produced electrode assembly into a cylindrical battery can, an electrolytic solution was injected to produce a 4680 cell.

[0438] At this time, for the negative electrode, a negative electrode active material (graphite:SiO = 95:5 (weight ratio) mixture), a conductive material (Super C), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed in water at a weight ratio of 96:2:1.5:0.5 to produce a negative electrode slurry. Then, the negative electrode slurry was applied to one surface of a copper current collector sheet, dried at 150 °C, and then rolled to produce it.

[0439] Regarding the 4680 cell manufactured in this way, charging it to 4.2 V at 0.5C at 40 °C and then discharging it to 2.5 V at 0.5C was defined as one cycle, and after performing 50 cycles of charge and discharge, the capacity retention rate and the resistance (DCIR) increase rate were measured. The measurement results are shown in Fig. 33b.

[0440] Referring to Fig. 33b, it can be seen that in the case of the secondary batteries of Example 3-1 and 3-3, the change in the capacity retention rate according to the number of cycles is small compared to the secondary battery of Comparative Example 3-1, and the change in the resistance increase rate according to the number of cycles is also small.

[0441] As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited thereto, and it goes without saying that various modifications and variations can be made within the equivalent scope of the technical idea of the present invention and the claims by those having ordinary knowledge in the technical field to which the present invention pertains.

Explanation of Signs

[0442] 10 Positive electrode 10a Positive electrode non-coated part 11 Negative electrode 11a Negative electrode non-coated part 12 Separator 13 First electrode tab 14 Second electrode tab 20 Current collector 21 Active material layer 22 Plain part 23 Beading part 24 Crimping part 30 Current collecting plate 31 Current collecting plate 35 Insulating gasket 35a Gasket exposed part 35b Gasket insertion part 36 First current collecting plate 37 Insulator 38 Second current collecting plate 38a Sub-plate 38b Outer end part 39 Sealing gasket 41 Bending part 43 Crimping part 44 Beading part 45 Lead 46 Insulator 49a Terminal exposed part 49b Terminal insertion part 50 Electrode terminal 50a Body part 50b External flange part 50c Internal flange part 50d Flat part 51 Battery housing 51a Inner peripheral surface 52 Bottom part 52a Outer surface 52b Inner surface 53 Through hole 54 Insulating gasket 54a External gasket 54b Internal gasket 55 Indentation Part 55a Side wall 55b Inclined surface 56 Inner edge 57 Opposing surface 60 Cap plate 70 Cylindrical battery 71 Electrode assembly 72 First plain part 73 Second non-coated part 74a Cap plate 74b Sealing gasket 75 Crimping part 76 Beading part 76a Inner peripheral surface 77 Bending part 78 First current collector 79 Second current collector 79a Central part 79a Part 80 Cavity 80a Welding hole 90 Electrode 91 Current collector 92 Active material layer 93 Non-coated part 93’ Core side non-coated part 93a Divided slice 94 Insulating coating layer

Claims

1. An electrode assembly in which a first electrode, a second electrode, and a separation membrane interposed therebetween are wound around a winding axis to define a core and an outer peripheral surface, wherein the first electrode and the second electrode each include a first plain portion and a second plain portion along the winding direction where an active material layer is not coated, and the first plain portion and the second plain portion are each defined as an electrode tab by themselves, and an electrode assembly; A battery housing that houses the electrode assembly through an opening formed on one side and is electrically connected to the second plain portion; An electrode terminal that is riveted through a through hole formed in a closing portion provided on the side opposite to the opening of the battery housing and is electrically connected to the first plain portion; A cap plate configured to cover the opening of the battery housing, and includes: The electrode terminal is A main body portion inserted into the through hole; An external flange portion extending along the outer surface of the closing portion from one side peripheral edge of the main body portion exposed on the outer surface of the closing portion of the battery housing; An internal flange portion extending toward the inner surface of the closing portion in a plan view along the inner surface from the other side peripheral edge of the main body portion exposed on the inner surface of the closing portion; A flat portion provided inside the internal flange portion, and includes a cylindrical battery.

2. The cylindrical battery according to claim 1, wherein the cap plate is insulated from the battery housing and has no polarity by not being electrically connected to the electrode assembly.

3. The surface of the electrode terminal exposed outside the battery housing is a first electrode terminal, The cylindrical battery according to claim 1 or 2, wherein a portion of the outer surface of the closing portion of the battery housing that is parallel to the upper surface of the first electrode terminal is a second electrode terminal.

4. The cylindrical battery according to claim 1 or 2, wherein the flat portion and the inner surface of the closing portion are parallel to each other.

5. The cylindrical battery according to claim 1 or 2, wherein an angle between the internal flange portion and the inner surface of the closing portion is 0° to 60°.

6. A recessed portion having a structure of an asymmetric groove is provided between the internal flange portion and the flat portion, The cylindrical battery according to claim 1 or 2, wherein the asymmetric groove includes a side wall of the flat portion and an inclined surface of the internal flange portion connected to an end portion of the side wall.

7. The cylindrical battery according to claim 6, wherein the side wall is perpendicular to the inner surface of the closing portion.

8. The cylindrical battery according to claim 1 or 2, wherein the thickness of the inner flange portion decreases as it is farther from the main body portion.

9. The cylindrical battery according to claim 1 or 2, further comprising an insulating gasket interposed between the electrode terminal and the through hole.

10. The insulating gasket includes an external gasket interposed between the external flange portion and the outer surface of the closing portion, and an internal gasket interposed between the inner flange portion and the inner surface of the closing portion, and the cylindrical battery according to claim 9, wherein the internal gasket and the external gasket have different thicknesses depending on the position.

11. The cylindrical battery according to claim 10, wherein the thickness of the region interposed between the inner edge of the through hole connected to the inner surface of the closing portion and the inner flange portion in the region of the inner gasket is relatively thinner than other regions.

12. The cylindrical battery according to claim 11, wherein the inner edge of the through hole includes a facing surface facing the inner flange portion.

13. The cylindrical battery according to claim 10, wherein the inner gasket extends longer than the inner flange portion.

14. The cylindrical battery according to claim 10, wherein the height of the flat portion is higher than or the same as the height of the end portion of the inner gasket with reference to the inner surface of the closing portion.

15. The cylindrical battery according to claim 1 or 2, wherein the height of the flat portion is higher than or the same as the height of the end portion of the inner flange portion with reference to the inner surface of the closing portion.

16. The cylindrical battery according to claim 1 or 2, wherein the radius from the center of the main body portion to the periphery of the external flange portion is 10% to 60% based on the radius from the center of the main body portion to the periphery of the closing portion.

17. The cylindrical battery according to claim 1 or 2, wherein the radius from the center of the main body portion to the periphery of the flat portion is 4% to 30% based on the radius from the center of the main body portion to the periphery of the closing portion.

18. The first plain portion includes a plurality of divided sections that can be independently bent, and the plurality of divided sections of the first plain portion form a bent surface of the divided section at one end of the electrode assembly while being bent toward the core side. The cylindrical battery according to claim 1 or 2, wherein the electrode terminal is electrically connected to the folded surface of the divided section of the first non-patterned portion.

19. A first current collector plate coupled to the folded surface of the divided section of the first non-patterned portion; An insulator interposed between the first current collector plate and the inner surface of the closed portion, further comprising: The insulator includes a hole for exposing the flat portion of the electrode terminal to the first current collector plate; The cylindrical battery according to claim 18, wherein the flat portion of the electrode terminal passes through the hole of the insulator and is coupled to the first current collector plate.

20. The second non-patterned portion includes a plurality of independently foldable divided sections; The plurality of divided sections of the second non-patterned portion form a folded surface of the divided section at the other end of the electrode assembly while being folded toward the core side; The cylindrical battery according to claim 1 or 2, wherein the battery housing is electrically connected to the folded surface of the divided section of the second non-patterned portion.

21. Further comprising a second current collector plate coupled to the folded surface of the divided section of the second non-patterned portion; At least a part of the periphery of the second current collector plate extends toward the inner surface of the beading portion and is interposed and fixed between the inner surface of the beading portion and the sealing gasket. The cylindrical battery according to claim 20.

22. A first slide portion in which the thickness of the active material layer decreases in the boundary region between the patterned portion and the non-patterned portion of the first electrode, and a second slide portion in which the thickness of the active material layer decreases in the boundary region between the patterned portion and the non-patterned portion of the second electrode; The first slide portion and the second slide portion are located in opposite directions in the winding axis direction; The cylindrical battery according to claim 1 or 2, wherein the patterned portion of the first electrode includes a loading reduction portion in which the loading amount of the active material decreases, and the position of the loading reduction portion corresponds to the position of the second slide portion.

23. The active material layer of the first electrode includes a positive electrode active material including single particles, pseudo single particles, or a combination thereof; The minimum particle size Dmin appearing in the volume cumulative distribution of the positive electrode active material is 1.0 μm or more; The particle size D50 when the volume cumulative amount is 50% in the volume cumulative distribution of the positive electrode active material is 5.0 μm or less; The cylindrical battery according to claim 1 or 2, wherein the maximum particle size Dmax appearing in the volume cumulative distribution of the positive electrode active material is 12 μm to 17 μm.

24. The positive electrode active material has a unimodal particle size distribution in which a single peak appears in the volume cumulative particle size distribution graph, and the following Mathematical Formula 1 [Mathematical Formula 1] Particle size distribution (PSD) = (Dmax - Dmin) / D50 The cylindrical battery according to claim 23, wherein the particle size distribution (PSD) represented by the formula is 3 or less.

25. The cylindrical battery according to claim 23, wherein the single particle, pseudo single particle, or a combination thereof is contained in an amount of 95 wt% to 100 wt% based on the total weight of the positive electrode active material contained in the active material layer of the first electrode.

26. The cylindrical battery according to claim 23, wherein the positive electrode active material contains a lithium nickel-based oxide containing Ni in an amount of 80 mol% or more based on the total number of moles of transition metals.

27. The porosity of the active material layer of the first electrode is 15% to 23%, The cylindrical battery according to claim 23, wherein the active material layer of the first electrode contains flaky graphite in a weight ratio of 0.05 wt% to 5 wt%.

28. The cylindrical battery according to claim 23, wherein the active material layer of the first electrode further contains carbon nanotubes.

29. The active material layer of the second electrode contains a silicon-based negative electrode active material and a carbon-based negative electrode active material, The cylindrical battery according to claim 23, wherein the silicon-based negative electrode active material and the carbon-based negative electrode active material are contained in a weight ratio of 1:99 to 20:

80.

30. A battery pack including a plurality of the cylindrical batteries according to claim 1 or 2.

31. An automobile including the battery pack according to claim 30.

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