CN118591916A - Wound electrode assembly, battery cell including the same, and cylindrical battery - Google Patents

Abstract

The winding-type electrode assembly according to an embodiment of the present invention includes: a positive plate; a negative electrode sheet; and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein a portion of the separator facing one end of the positive electrode sheet located inside the wound electrode assembly includes a first separator portion facing the negative electrode sheet and a second separator portion facing the positive electrode sheet, and a friction coefficient between the first separator portion and the negative electrode sheet is smaller than a friction coefficient between the second separator portion and the positive electrode sheet.

Description

Wound electrode assembly, battery cell including the same, and cylindrical battery

Cross Reference to Related Applications

The present application claims the benefits of korean patent application No.10-2022-0032953, filed on 3 months 16 of 2022, and korean patent application No.10-2023-0032949, filed on 14 months 3 of 2023, to the korean intellectual property office, the entire contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates to a winding-type electrode assembly, a battery cell and a cylindrical battery including the same, and more particularly, to a winding-type electrode assembly in which an inner loop is prevented, a battery cell and a cylindrical battery including the same.

Background

In modern society, with the daily use of portable devices such as mobile phones, notebook computers, video cameras, and digital cameras, technological development in the fields related to mobile devices as described above has been initiated. In addition, chargeable/dischargeable secondary batteries are used as power sources for Electric Vehicles (EVs), hybrid Electric Vehicles (HEVs), plug-in hybrid electric vehicles (P-HEVs), and the like, in an attempt to solve problems of air pollution and the like caused by existing gasoline vehicles using fossil fuel. Accordingly, the demand for developing secondary batteries is increasing.

The secondary batteries commercialized at present include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium secondary batteries. Among them, a lithium secondary battery has been focused on because it has advantages such as free charge and discharge, and very low self-discharge rate and high energy density.

Lithium secondary batteries are also classified into cylindrical, prismatic or pouch shapes according to the shape of an external material in which an electrode assembly is received. The electrode assemblies are broadly classified into: a winding type configured to have a structure in which a long-sheet cathode and a long-sheet anode to which an active material is applied are wound in a state in which a separator is disposed between the cathode and the anode; a stack type configured to have a structure in which a plurality of cathodes and a plurality of anodes having predetermined dimensions are sequentially stacked in a state in which separators are respectively disposed between the cathodes and the anodes; and a stacking/folding type constructed in a structure in which the stacking type unit cells are wound with a long separation film. Among them, the winding type has advantages in that the winding type is easy to manufacture and has high energy density per unit weight.

Such a rolled electrode assembly is manufactured by: the separator is interposed between the cathode and the anode, and then wound into a cylindrical shape. The winding process is performed by: the separator and the electrode were wound on a mandrel divided into two parts, and then the mandrel was removed from the electrode assembly.

Fig. 1 is a perspective view of a conventional roll-type electrode assembly. Fig. 2 is an enlarged view of section 'U' of fig. 1. Fig. 3 is a schematic view for explaining a change in electrode length in a conventional electrode assembly. Here, the partial enlarged view of fig. 2 shows that the central portion C of the electrode assembly is deformed after charge and discharge.

Referring to fig. 1 to 3, a conventional roll-type electrode assembly may be formed by winding a cathode 10 and an anode 20. In the wound electrode assembly, the cathode tab 11 attached to the cathode 10 and the anode tab 21 attached to the anode 20 may protrude in directions facing each other. In the wound electrode assembly, a separator is interposed between the cathode 10 and the anode 20.

The cathode 10 may have a free edge. When the cathode tab 11 is not located at the end of the cathode sheet, one end of the cathode 10 may be disposed in a state of having a coating layer coated with an active material, which may be referred to as a free edge portion 10A. A step may be formed around the central portion C of the electrode assembly by the free edge portion 10A. As the electrode assembly expands or contracts during the charge and discharge of the battery cells, the peripheral edge of the central portion C of the electrode assembly may be deformed, as shown in the partial enlarged view of fig. 2.

More specifically, referring to fig. 3, as the electrode assembly expands or contracts during the charge and discharge of the battery cell, the electrode length may change. During this process, the sliding may be restricted according to the frictional force between the electrodes 10 and 20 and the separator 30, and the anode 20 facing the free edge portion 10A may cause a buckling phenomenon (collision) due to a step or the like. If this phenomenon is repeated, the separator 30 between the cathode 10 and the anode 20 may be damaged, and breakage or internal disconnection of the electrode assembly may be caused, which seriously impairs the safety of the battery cell.

Disclosure of Invention

Technical problem

An object of the present disclosure is to provide a winding-type electrode assembly in which an internal disconnection problem of the electrode assembly due to a change in the electrode length during the charge of the battery cell is improved, a battery cell including the same, and a cylindrical battery.

However, the problems to be solved by the embodiments of the present disclosure are not limited to the above-described problems, and various extensions can be made within the scope of the technical ideas included in the present disclosure.

Technical solution

According to an embodiment of the present disclosure, there is provided a winding type electrode assembly including a cathode sheet, an anode sheet, and a separator sheet interposed between the cathode sheet and the anode sheet, wherein a separator sheet portion facing one end of the cathode sheet located inside the winding type electrode assembly includes a first separator sheet portion facing the anode sheet and a second separator sheet portion facing the cathode sheet, and wherein a friction coefficient between the first separator sheet portion and the anode sheet is smaller than a friction coefficient between the second separator sheet portion and the cathode sheet.

One end portion of the cathode sheet may be formed of a free edge portion containing an active material.

The free edge portion may include a portion where one end of the cathode sheet is coated with a cathode active material on the current collector.

One end of the anode tab may be located inside the wound electrode assembly as compared to one end of the cathode tab.

The rolled electrode assembly further includes a sliding layer between the first separator portion and the anode sheet, wherein a friction coefficient between the sliding layer and the first separator portion or a friction coefficient between the sliding layer and the anode sheet may be smaller than a friction coefficient between the second separator portion and the cathode sheet.

One end portion of the cathode sheet is formed of a free edge portion containing an active material, and a sliding layer may be located on the first separator portion covering the free edge portion.

Based on the cross section of the rolled electrode assembly, the free edge portion may be located between both end portions of the sliding layer.

The length of the sliding layer may be 10mm to 30mm.

The sliding layer may be made of a porous material.

The rolled electrode assembly may further include a barrier layer positioned to face the free edge portion between the separator sheet and the cathode sheet.

The barrier layer may be located on the second separator sheet portion so as to cover the free edge portion.

The coefficient of friction between the barrier layer and the second separator sheet portion or the coefficient of friction between the barrier layer and the cathode sheet may be greater than the coefficient of friction between the first separator sheet portion and the anode sheet.

The wound electrode assembly may further include a separator overlapping portion formed on the separator portion, the separator portion overlapping one end portion of the cathode sheet in a direction from an outer side to an inner side of the wound electrode assembly.

The separator overlapping portion is formed between one end of the cathode sheet and the anode sheet, and the thickness of the separator overlapping portion may be formed thicker than the thickness of the separator portion not facing one end of the cathode sheet.

The separator includes a first separator located on one surface of the cathode sheet and a second separator located on the other surface of the cathode sheet, and the separator overlapping portion may include one end portion of the first separator and one end portion of the second separator, the one end portion of the first separator being formed by bending at least twice in the same direction such that the first separator covers a cut surface of the one end portion of the cathode sheet, and the one end portion of the second separator overlaps the one end portion of the first separator.

One end portion of the second separator sheet may include a double layer by bending the end portion at least twice.

According to another embodiment of the present disclosure, there is provided a battery cell including: a rolled electrode assembly and a battery case accommodating the rolled electrode assembly.

According to still another embodiment of the present disclosure, there is provided a cylindrical battery including the above-described battery cell.

Advantageous effects

According to embodiments, the electrode assembly of the present disclosure may minimize friction between the electrode and the separator, thereby preventing the internal disconnection of the wound electrode assembly and improving the safety of the battery cell.

The advantageous effects of the present disclosure are not limited to the above-described effects, and additional other effects not described above will be clearly understood by those skilled in the art from the description of the appended claims.

Drawings

Fig. 1 is a perspective view of a conventional wound electrode assembly;

FIG. 2 is an enlarged view of section 'U' of FIG. 1;

Fig. 3 is a view for explaining a change in the length of an electrode in a conventional electrode assembly;

Fig. 4 is a perspective view of an electrode assembly according to an embodiment of the present disclosure;

fig. 5 is an exploded perspective view illustrating a state before the electrode assembly of fig. 4 is wound;

FIG. 6 is a diagram showing an electrode and a separator positioned around a free edge portion;

Fig. 7 is a diagram illustrating a modified embodiment of the electrode assembly of fig. 6;

fig. 8 is a view illustrating another modified embodiment of the electrode assembly of fig. 6;

fig. 9 is a diagram illustrating an electrode assembly according to another embodiment of the present disclosure; and

Fig. 10 is a diagram illustrating an electrode assembly according to still another embodiment of the present disclosure.

Detailed Description

Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the various embodiments. The present disclosure may be modified in various different ways and is not limited to the embodiments set forth herein.

For clarity of description of the concepts of the present invention, parts irrelevant to the description are omitted, and like reference numerals denote like elements throughout the description.

In addition, the size and thickness of each component shown in the drawings are arbitrarily enlarged or reduced for better understanding and convenience of description, but the inventive concept is not limited thereto. In the drawings, the thickness of layers and regions, etc. are exaggerated for clarity of presentation of the respective layers and regions. The thickness of some layers and regions are exaggerated for better understanding and ease of description. Furthermore, it will be understood that when an element such as a layer, film, region or panel is referred to as being "on" or "over" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element such as a layer, film, region or plate is referred to as being "directly on" another element, it means that there are no other intervening elements present. Further, the word "upper" or "above" means being arranged on or below the reference portion, and does not necessarily mean being arranged on an upper end portion of the reference portion that is directed to the opposite direction of gravity. Meanwhile, similarly to the case where it is described as being located "on" or "above" another portion, the case where it is described as being located "under" or "below" another portion will also be understood with reference to the above.

Furthermore, throughout the description, when a portion is referred to as "comprising" or "including" a certain component, unless otherwise specified, it is intended that the portion may also include other components without excluding other components.

Further, in the entire description, when referred to as a "plane", this means that the target portion is viewed from the upper side, and when referred to as a "cross section", this means that the target portion is viewed from the side of the vertically cut cross section.

Fig. 4 is a perspective view of an electrode assembly according to an embodiment of the present disclosure. Fig. 5 is an exploded perspective view illustrating a state before the electrode assembly of fig. 4 is wound.

An electrode assembly according to an embodiment of the present disclosure is described below.

Referring to fig. 4 and 5, the wound electrode assembly 50 of the present embodiment may include a cathode tab 100, an anode tab 200, and a separator 300 interposed between the cathode tab 100 and the anode tab 200. The cathode tab 100, the anode tab 200, and the separator tab 300 may be alternately stacked to form a tab-shaped stack. The sheet stack may be wound by an elongated rod-shaped winding mandrel. Here, the cathode tab 100 and the anode tab 200 may be collectively referred to as electrode tabs 100 and 200.

Meanwhile, at the central portion C of the wound electrode assembly 50, the anode tab 200 may be wound to extend from the cathode tab 100. That is, after the anode tab 200 and the separator 300 are first wound, the cathode tab 100 may be further provided to the anode tab 200 and the separator 300 and wound together. In consideration of the chemical reaction of the lithium ion battery, since the anode receives lithium ions of the cathode, the length and width of the anode sheet 200 may be preferably formed to be greater than those of the cathode sheet 100 to smoothly charge and discharge. Therefore, it may be preferable that the anode sheet 200 is wound earlier than the cathode sheet 100 in the winding of the wound electrode assembly. Thus, the anode tab 200 is located at the innermost side of the central portion C, and one end of the cathode tab 100 may be located at the outer side (left side in fig. 6) as compared to the anode tab 200. In other words, one end portion of the anode tab 200 may be positioned closer to the central portion C of the electrode assembly 50 than one end portion of the cathode tab 100. The central portion C of the electrode assembly 50 may be the inner side shown in fig. 6.

One end of the anode tab 200 may be located inside the central portion C of the electrode assembly 50 as compared to one end of the cathode tab 100. Further, the other end portion of the anode tab 200 located on the outer circumferential surface of the electrode assembly 50 may also be extendedly disposed to cover the other end portion of the cathode tab 100. Here, the central portion C of the electrode assembly 50 may refer to a radial central portion based on a cross section of the wound electrode assembly.

The electrode sheets 100 and 200 may be obtained by coating a slurry containing an electrode active material onto a current collector. The cathode sheet 100 may include a coating portion 130 coated with a paste and an uncoated portion 120 uncoated with a paste, and the anode sheet 200 may include a coating portion 230 coated with a paste and an uncoated portion 220 uncoated with a paste. Further, the cathode tab 110 may be located on the uncoated portion 120 of the cathode sheet 100, and the anode tab 210 may be located on the uncoated portion 220 of the anode sheet 200. The cathode tab 110 and the anode tab 210 may protrude in a direction facing each other in a height direction (x-axis direction of fig. 5) of the electrode assembly. However, it may be formed in a different manner according to design.

Here, the electrode paste may generally include an electrode active material, a conductive material, a binder, and a solvent, but is not limited thereto. Here, the current collector may be made of stainless steel, aluminum, copper, nickel, titanium, calcined carbon, etc., and may be provided in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, or a nonwoven. Examples of the current collector for the cathode sheet 110 include aluminum or an alloy thereof, and examples of the current collector for the anode sheet 200 include copper, nickel, stainless steel, or an alloy of any one thereof.

The separation sheet 300 may separate between the cathode sheet 100 and the anode sheet 200 and provide a moving path of ions moving between the cathode sheet 100 and the anode sheet 200. The separator 300 is a main component determining the performance of the secondary battery. In order for the separator 300 to have physical properties suitable for the secondary battery, the physical properties such as minimizing thickness to reduce resistance and maximizing porosity and pore size must be satisfied. In addition, electrochemical properties such as wettability with the electrolyte solution must also be satisfied.

The coating material may be coated on one surface or both surfaces of the separator 300 to form a coating layer, and heat resistance and safety of the separator 300 may be improved by the coating layer. For example, a coating material including alumina (Al ₃O₂) and a binder may be coated on one surface or both surfaces of the fabric of the separator 300. When the fabric is coated with highly heat-resistant alumina, the separator 300 may physically interrupt contact between the cathode and the anode even under high temperature conditions inside the battery cell such as thermal runaway, thereby preventing internal short circuits of the battery cell.

The coating layer of separator 300 can include ceramic particles and a polymeric binder. An example of the ceramic particles may be alumina, and the characteristics of the separator 300 may vary according to the diameter of the alumina. For example, the smaller the diameter of the alumina, the lower the coefficient of friction of the coating layer. As the diameter of the alumina decreases, the surface area of the particles increases, and a relatively large number of particles may contact the fabric of the separator 300, thereby improving the adhesion of the particles and inhibiting the deformation of the separator 300. In addition, even when the coating material is repeatedly applied to the fabric of the separator 300, if the particle diameter is small, the thickness of the coating layer is reduced. Accordingly, the gas permeability of the coating layer may be increased, and the ion-conducting resistance of the separator 300 may be reduced, as compared to the case where the diameter of the particles is large.

The coating layer may vary according to the coating material forming the coating layer, but when the coating layer is formed using a coating material having a higher friction coefficient than the separator fabric, the coating layer may be formed on one surface of the separator 300 facing the cathode sheet 100. Alternatively, coating layers may be formed on both surfaces of the separator 300, respectively. At this time, the friction coefficient of the first coating layer formed on one surface of the separator sheet 300 facing the anode sheet 200 may be designed to be smaller than that of the second coating layer formed on the other surface of the separator sheet 300 facing the cathode sheet 100. In order to make the coefficient of friction of the first coating layer and the coefficient of friction of the second coating layer different from each other, the diameter of the ceramic particles as described above may be adjusted.

Meanwhile, one end portion of the cathode sheet 100 may have a free edge portion 100A. One end portion of the cathode sheet 100 may be formed of the coated portion 130 instead of the uncoated portion 120, and such an end portion may be referred to as a free edge portion or a coated edge portion, or the like. As shown in fig. 5, according to the present embodiment, the cathode tab 110 may not be located at one end portion of the cathode sheet 100, but may be located at a central portion. Thus, this end may be referred to as the free edge portion 100A in the following sense: the cathode tab 110 is not located at one end of the cathode tab 100 or an uncoated portion 120 for positioning the cathode tab 110 is not formed. Alternatively, since one end portion of the cathode sheet 100 is formed of the coating portion 130 and the coating layer is not cut, the end portion may be referred to as a coating edge portion. Here, one end of the cathode sheet 100, on which the free edge portion or the coated edge portion is formed, may be a core of the wound electrode assembly. Thus, the cathode tab 110 may not be positioned around the central portion C of the electrode assembly.

The free edge portion 100A is formed at one end portion of the cathode sheet 100 in such a manner that a phenomenon in which a portion of the anode sheet facing the free edge portion is bent during volume expansion of the electrode assembly may occur, which may cause a problem in that the separator 300 is damaged. However, in the electrode assembly of the present embodiment, the above-described problems may be solved by varying the friction level between the separator 300 and the electrode sheets 100 and 200.

Fig. 6 is a view showing the electrode and the separator positioned around the free edge portion described above. Fig. 7 is a diagram illustrating a modified embodiment of the electrode assembly of fig. 6. Fig. 8 is a view illustrating another modified embodiment of the electrode assembly of fig. 6.

In the electrode assembly according to the present embodiment of fig. 6, the electrode sheets 100 and 200 and the separator 300 surrounding the free edge portion 100A are in a wound state, but in fig. 6, for convenience of explanation, the electrode sheets 100 and 200 and the separator 300 are shown to be flat, and the electrode sheets 100 and 200 and the separator 300 are shown to be in a state in which they are not in close contact with each other. In fig. 6, the anode tab 200 disposed above and below the cathode tab 100 may be wound earlier or later than the cathode tab 100 when the electrode assembly is wound.

Referring to fig. 6, in the electrode assembly of the present embodiment, the separator 300 may have a separator portion facing the free edge portion 100A, the free edge portion 100A corresponding to one end of the cathode sheet 100 located inside the wound electrode assembly. Here, facing the free edge portion 100A may mean overlapping each other in a direction toward the central portion C of the rolled electrode assembly 50 of fig. 4. In other words, the portion of the separator overlapping the free edge portion 100A in the z-axis direction in fig. 5 and 6 may include a first separator portion facing the anode sheet 200 and a second separator portion facing the cathode sheet 100.

The cathode tab (110 shown in fig. 5) according to the present embodiment is formed at a position distant from the central portion C of the electrode assembly 50 shown in fig. 4 (see fig. 5). The central portion C of the electrode assembly may be located at one side of the y-axis direction in which the free edge portion 100A is located in fig. 5 and 6. Accordingly, the coating portion 130 of fig. 5 is formed on the current collector of the cathode sheet 100 up to one end portion of the cathode sheet 100 adjacent to the central portion C of the electrode assembly, and the free edge portion 100A may refer to a portion at one end portion of the cathode sheet 100 where the coating portion 130 is formed on the current collector of the cathode sheet 100. In other words, one end of the free edge portion 100A may have a shape in which the coating portion 130 is cut.

The portion of the separator sheet corresponding to the free edge portion 100A may have a width within the first range T1 based on one end edge of the cathode sheet 100. The separator sheet 300 may include a first surface 300A facing the anode sheet 200 and a second surface 300B facing the cathode sheet 100. The portion of the separator 300 may include a first separator portion facing the anode sheet 200 and a second separator portion facing the cathode sheet 100. The first separator section can include a first surface 300A and the second separator section can include a second surface 300B.

In the present embodiment, the coefficient of friction between the first surface 300A of the first separator portion and the anode sheet 200 may be different from the coefficient of friction between the second surface 300B of the second separator portion and the cathode sheet 100. Specifically, the coefficient of friction between the first surface 300A of the first separator and the anode sheet 200 may be smaller than the coefficient of friction between the second surface 300B of the second separator portion and the cathode sheet 100. The friction coefficient between the anode tab 200 and the first separator portion of the separator 300 having the first surface 300A positioned around the free edge portion 100A is formed in a relatively small size in this way so as to be able to slide between the separator 300 and the anode tab 200 and to prevent the bending phenomenon of the anode tab 200 and the internal disconnection of the electrode assembly caused thereby. That is, during expansion of the electrode assembly, the anode tab 200 may slide better than the cathode tab 100. Therefore, when the length of the electrode tab increases as the electrode assembly expands while the battery cell is charged, it is possible to prevent the phenomenon in which the end portion of the anode tab 200 is bent.

In the present embodiment, the relative friction coefficient is adjusted in different manners, and thus, the magnitude of the above friction coefficient can be compared by a conventional friction coefficient measuring method and a friction coefficient measuring apparatus.

The separator 300 may be provided in various ways.

As described above, in order to relatively reduce the friction coefficient between the anode sheet 200 and the first separator portion having the first surface 300A of the separator 300 positioned around the free edge portion 100A, the surface roughness may also be adjusted. As an example, coating layers may be formed on both surfaces of the separator 300. The surface roughness of the first surface 300A and the surface roughness of the second surface 300B may be differently formed according to the coating layer formed on each surface. When the coating layer includes ceramic particles, the ceramic particles of the coating layer formed on the first surface 300A and the ceramic particles of the coating layer formed on the second surface 300B may have different diameters. The diameter of the ceramic particles of the coating layer formed on the first surface 300A may be smaller than the diameter of the ceramic particles of the coating layer formed on the second surface 300B.

As another example, the coating layer is formed on only one surface of the separator 300 such that the surface roughness of the first surface 300A and the surface roughness of the second surface 300B may be differently formed. When the surface roughness of the coating layer is smaller than that of the fabric of the separator 300, a coating layer may be formed on the first surface 300A. When the surface roughness of the coating layer is greater than that of the fabric of the separator 300, a coating layer may be formed on the second surface 300B.

As another example, a coating layer may not be formed on the separator 300. The surface roughness of the first surface 300A and the surface roughness of the second surface 300B of the separator sheet 300 may vary according to the characteristics of the separator fabric. At this time, the first surface 300A may be a surface having a relatively low surface roughness in the spacer fabric, and the second surface 300B may be a surface having a relatively large surface roughness in the spacer fabric.

In the present embodiment, since the relative surface roughness is adjusted in different manners, the magnitude of the above-described surface roughness can be compared by a conventional surface roughness measuring method and a surface roughness measuring apparatus.

Referring to fig. 7, an electrode assembly according to another embodiment of the present embodiment may be provided with a sliding layer 400.

The sliding layer 400 is disposed between the first separator portion, which is the separator 300 surrounding the free edge portion 100A, and the anode sheet 200, thereby enabling sliding between the separator 300 and the anode sheet 200. The sliding layer 400 may have a lower coefficient of friction than the separator 300. Specifically, the friction coefficient between the sliding layer 400 and the first separator portion or the friction coefficient between the sliding layer 400 and the anode sheet 200 may be smaller than the friction coefficient between the second separator portion and the cathode sheet 100. The sliding layer 400 may be attached to the anode sheet 200 or the first separator sheet portion using a material that can adhere at room temperature. When the sliding layer 400 is attached to the anode tab 200, a friction coefficient between the sliding layer 400 and the first separator portion may be smaller than a friction coefficient between the second separator portion and the cathode tab 100. When the sliding layer 400 is attached to the first separator portion, the friction coefficient between the sliding layer 400 and the anode sheet 200 may be smaller than the friction coefficient between the second separator portion and the cathode sheet 100.

The sliding layer 400 may be made of a porous material. The sliding layer 400 includes a plurality of holes, so that it does not hinder movement of lithium ions or charges between the cathode sheet 100 and the anode sheet 200. If the sliding layer 400 is not made of a porous material, a short problem due to lithium precipitation may occur. Examples of materials that may be used for the sliding layer 400 include Polyethylene (PE), polypropylene (PP), etc., and materials for the fabric of the separator 300 may be suitable for the sliding layer 400. Alternatively, the sliding layer 400 may be used so as to have a ceramic coating layer on the fabric surface of the separator 300.

The sliding layer 400 may be disposed around the free edge portion 100A. The sliding layer 400 may be positioned to correspond to the free edge portion 100A. Here, corresponding to the free edge portion 100A may mean overlapping each other in a direction toward the central portion C of the rolled electrode assembly.

The sliding layer 400 may be located on the first surface 300A of the separator 300 covering the free edge portion 100A, the sliding layer 400 not being in contact with the free edge portion 100A.

Since the cathode tab 100 repeatedly expands or contracts according to the charge and discharge of the battery cell including the electrode assembly, the sliding layer 400 may be provided in consideration of the varying positions of the free edge portion 100A. Specifically, as shown in fig. 7, the position of the free edge portion 100A may vary within the first range T1 according to the expansion or contraction of the cathode sheet 100. At this time, the first length L1, which is the length of the sliding layer 400, is set to a length greater than the first range T1, thereby allowing the sliding layer 400 and the free edge portion 100A to correspond to each other. When the first wound portion is defined as the inner side and the second wound portion is defined as the outer side in the direction in which the cathode sheet 100, the anode sheet 200, or the separator sheet 300 extends, one end portion of the sliding layer 400 is located inside the free edge portion 100A, and the other end portion of the sliding layer 400 may be located outside the free edge portion 100A. The sliding layer 400 is disposed such that the free edge portion 100A is located between both end portions of the sliding layer 400 in a direction in which the cathode sheet 100, the anode sheet 200, or the separator sheet 300 extends. Based on the cross section of the wound electrode assembly, the sliding layer 400 may be disposed such that the free edge portion 100A is located between both ends of the sliding layer 400. At this time, the cross section of the wound electrode assembly refers to the surface shown in fig. 6, and may be a surface perpendicular to the central axis of the electrode assembly. Here, both end portions of the sliding layer 400 may be end portions in a longitudinal direction, which may be a direction in which the cathode tab 100, the anode tab 200, or the separator tab 300 extends.

As a specific example, the first length L1 of the sliding layer 400 may range from 10mm to 30mm or from 15mm to 25mm. Alternatively, the first length L1 of the sliding layer 400 may be about 20mm. Here, the first length L1 may be calculated based on the direction in which the cathode tab 100, the anode tab 200, or the separator tab 300 extends. Here, the first length L1 may be calculated based on a direction perpendicular to the height direction of the electrode assembly.

Referring to fig. 8, a barrier layer 400' according to the present embodiment may be disposed between the cathode sheet 100 and the separator sheet 300, unlike the sliding layer disposed between the separator sheet 300 and the anode sheet 200 in the embodiment of fig. 7. The barrier layer 400' is positioned to correspond to the free edge portion 100A and may be located on the second separator portion 300 covering the free edge portion 100A so as to cover the free edge portion 100A. At this time, not only the barrier layer 400 'causes sliding between the separator 300 and the anode sheet 100, but also the separator 300 and the barrier layer 400' may be doubly disposed between the anode sheet 200 and the cathode sheet 100 to physically prevent internal short circuits. At this time, the friction coefficient between the barrier layer 400 'and the second separator sheet portion or the friction coefficient between the barrier layer 400' and the cathode sheet 100 is preferably greater than the friction coefficient between the first separator sheet portion and the anode sheet 200. This is because the internal short between the anode tab 200 and the cathode tab 100 can be prevented by the barrier layer 400', but the bending phenomenon of the anode tab 200 can also be prevented, so that the effect of preventing the internal short can be greatly improved.

Fig. 8 only shows the case where the barrier layer 400 'is disposed between the anode sheet 100 and the separator sheet 300, but as a modified embodiment, the sliding layer 400 between the anode sheet 200 and the separator sheet 300 and the barrier layer 400' between the cathode sheet 100 and the separator sheet 300 may be disposed together, as described in fig. 7.

Fig. 9 is a diagram illustrating an electrode assembly according to another embodiment of the present disclosure.

Referring to fig. 9, at least one sliding layer 400 of the two sliding layers 400 described with reference to fig. 7 is omitted, and a spacer overlapping portion 305P may be formed at a position where the sliding layer 400 is omitted. The separator overlapping portion 305P may be formed in the following portions of the separator sheet 300: this portion overlaps with one end portion of the cathode sheet 100 in a direction from the outside to the inside (central portion) of the wound electrode assembly. The separator overlapping portion 305P according to the present embodiment is formed between one end of the cathode sheet 100 and the anode sheet 200, wherein the thickness of the separator overlapping portion 305P may be formed thicker than the thickness of the separator portion that does not face one end of the cathode sheet 100.

The separator 305 according to the present embodiment may include a first separator 305a located on one surface of the cathode sheet 100 and a second separator 305b located on the other surface of the cathode sheet 100. The separator overlapping portion 305P may include one end portion of the first separator sheet 305a and one end portion of the second separator sheet 305b, the one end portion of the first separator sheet 305a being formed by bending at least twice in the same direction such that the first separator sheet 305a covers the cut surface 100C of the one end portion of the cathode sheet 100 and the one end portion of the second separator sheet 305b overlaps the one end portion of the first separator sheet 305 a. Here, one end portion of the first separation sheet 305a may be formed by bending to cover the free edge portion 100A. One end portion of the first separation sheet 305a may be bent twice to cover the upper surface, the side surface, and the lower surface of the free edge portion 100A.

One end portion of the second separation sheet 305b may include a double layer by bending the end portion at least twice. Specifically, the second separator sheet 305b may be bent in a direction toward the first separator sheet 305a, and bent again to overlap with the bent portion of the first separator sheet 305 a. One end portion of the second separation sheet 305b may include two layers. According to the present embodiment, by forming the separator overlapping portion 305P overlapping in three layers between the cathode tab 100 and the anode tab 200, an internal short circuit between the anode tab 200 and the cathode tab 100 can be physically prevented.

Further, the sliding layer 400 according to the present embodiment may include a spacer substrate layer 400a and an adhesive layer 400b, the adhesive layer 400b being formed on one surface of the spacer substrate layer 400 a. The adhesive layer 400b may be used to attach the sliding layer 400 to the anode sheet 200. The sliding layer 400 may further include a back-coating layer 400c, the back-coating layer 400c being located on a back surface of the separator substrate layer 400a in which the adhesive layer 400b is located. When the sliding layer 400 is wound in the form of a tape in preparation for attaching the sliding layer 400 to the anode sheet 200, the back coating layer 400c serves to prevent the adhesive layers 400b from adhering to each other.

The description of the sliding layer 400 herein may be applied to the sliding layer 400 described previously with reference to fig. 4 to 7.

Fig. 10 is a diagram illustrating an electrode assembly according to still another embodiment of the present disclosure.

The embodiment of fig. 10 is substantially the same as the embodiment described with reference to fig. 9, but the differences will be described below.

Referring to fig. 10, unlike the second separation sheet 305b described with reference to fig. 9, the second separation sheet 305c may not be bent. In other words, the second separator 305c according to the present embodiment may overlap the first separator 305a of fig. 9 without bending one end portion. Therefore, in the separator overlapping portion 305P according to the present embodiment, the double-overlapped separator overlapping portion 305P is formed between the cathode tab 100 and the anode tab 200, whereby an internal short circuit between the anode tab 200 and the cathode tab 100 can be physically prevented.

Except for the above-described differences, all the matters described with reference to fig. 9 are applicable to the present embodiment.

Meanwhile, the above-described wound electrode assembly according to the present embodiment may be received in a battery case to form a battery cell. Specifically, the rolled electrode assembly may be manufactured into a battery cell by: the wound electrode assembly is inserted into a cylindrical or prismatic metal container, an electrolyte solution is filled into the metal container, and the metal container is sealed. The battery cell including the wound electrode assembly may be a cylindrical battery or a prismatic battery, but the shape of the battery cell including the wound electrode assembly is not limited to the above-described examples.

Although the present invention has been described in detail hereinabove with reference to the preferred embodiments thereof, the scope of the present disclosure is not limited thereto and various modifications and improvements may be made by those skilled in the art using the basic concepts of the present disclosure, which modifications and improvements are defined in the appended claims, which also fall within the scope of the present disclosure.

Description of the reference numerals

100: Cathode plate

100A: free edge portion

110: Cathode tab

120: Uncoated portion

130: Coating part

200: Anode plate

300: Separating sheet

305: Separator overlapping portion

400: Sliding layer

400': Barrier layer

Claims (18)

1. A winding type electrode assembly includes a cathode sheet, an anode sheet, and a separator sheet interposed between the cathode sheet and the anode sheet,

Wherein the separator portion facing one end of the cathode sheet located inside the wound electrode assembly includes a first separator portion facing the anode sheet and a second separator portion facing the cathode sheet, and

Wherein a coefficient of friction between the first separator portion and the anode sheet is smaller than a coefficient of friction between the second separator portion and the cathode sheet.

2. The rolled electrode assembly of claim 1, wherein:

One end portion of the cathode sheet is formed of a free edge portion containing an active material.

3. The electrode assembly of claim 2, wherein:

The free edge portion includes a portion where one end portion of the cathode sheet is coated with a cathode active material on a current collector.

4. The rolled electrode assembly of claim 1, wherein:

one end of the anode tab is positioned at the inner side of the wound electrode assembly as compared to one end of the cathode tab.

5. The rolled electrode assembly according to claim 1,

Also comprises a sliding layer positioned between the first separation sheet part and the anode sheet,

Wherein a coefficient of friction between the sliding layer and the first separator portion or a coefficient of friction between the sliding layer and the anode sheet is smaller than a coefficient of friction between the second separator portion and the cathode sheet.

6. The rolled electrode assembly of claim 5, wherein:

One end portion of the cathode sheet is formed of a free edge portion containing an active material, and

The sliding layer is located on the first separator section covering the free edge section.

7. The rolled electrode assembly of claim 6 wherein:

The free edge portion is located between both end portions of the sliding layer based on a cross section of the rolled electrode assembly.

8. The rolled electrode assembly of claim 5, wherein:

the sliding layer has a length of 10mm to 30mm.

9. The rolled electrode assembly of claim 5, wherein:

the sliding layer is made of a porous material.

10. The rolled electrode assembly according to claim 1,

A barrier layer is also included and positioned to face the free edge portion between the separator sheet and the cathode sheet.

11. The rolled electrode assembly of claim 10, wherein:

the barrier layer is located on the second separator portion so as to cover the free edge portion.

12. The rolled electrode assembly of claim 11 wherein:

The coefficient of friction between the barrier layer and the second separator sheet portion or the coefficient of friction between the barrier layer and the cathode sheet is greater than the coefficient of friction between the first separator sheet portion and the anode sheet.

13. The rolled electrode assembly according to claim 1,

And a separator overlapping portion formed on the separator portion, the separator portion overlapping one end portion of the cathode sheet in a direction from an outside to an inside of the wound electrode assembly.

14. The electrode assembly of claim 13, wherein:

the separator overlapping portion is formed between one end portion of the cathode sheet and the anode sheet, and a thickness of the separator overlapping portion is formed thicker than a thickness of the separator portion not facing the one end portion of the cathode sheet.

15. The rolled electrode assembly of claim 14 wherein:

The separator sheet includes a first separator sheet on one surface of the cathode sheet and a second separator sheet on the other surface of the cathode sheet, and

The separator overlapping portion includes one end portion of the first separator sheet and one end portion of the second separator sheet, the one end portion of the first separator sheet being formed by bending at least twice in the same direction such that the first separator sheet covers a cut surface of the one end portion of the cathode sheet, and the one end portion of the second separator sheet overlaps the one end portion of the first separator sheet.

16. The rolled electrode assembly of claim 15 wherein:

one end portion of the second separator sheet includes a double layer by bending the end portion at least twice.

17. A battery cell, comprising:

the rolled electrode assembly according to claim 1, and

And a battery case accommodating the wound electrode assembly.

18. A cylindrical battery comprising the battery cell of claim 17.