KR20230135529A - Jelly roll type electrode assembly, battery cell including the same, and cylindrical battery - Google Patents

Abstract

A jelly roll-type electrode assembly according to an embodiment of the present invention is a jelly roll-type electrode assembly including a positive electrode sheet, a negative electrode sheet, and a separator sheet interposed between the positive electrode sheet and the negative electrode sheet, wherein the separator sheet unit facing one end of the negative electrode sheet positioned inside the jelly roll-type electrode assembly includes a first separator sheet unit facing the negative electrode sheet and a second separator sheet unit facing the positive electrode sheet, and the coefficient of friction between the first separator sheet unit and the negative electrode sheet is smaller than the coefficient of friction between the second separator sheet unit and the positive electrode sheet.

Description

Jelly roll-type electrode assembly, battery cell including the same, and cylindrical battery {JELLY ROLL TYPE ELECTRODE ASSEMBLY, BATTERY CELL INCLUDING THE SAME, AND CYLINDRICAL BATTERY}

The present invention relates to a jelly roll-type electrode assembly, a battery cell including the same, and a cylindrical battery, and more specifically, to a jelly roll-type electrode assembly that prevents internal short circuit, a battery cell including the same, and a cylindrical battery.

In modern society, as the use of portable devices such as mobile phones, laptops, camcorders, and digital cameras becomes routine, the development of technologies in fields related to the above mobile devices is becoming more active. In addition, secondary batteries that can be charged and discharged are a way to solve air pollution from existing gasoline vehicles that use fossil fuels, and are used in electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles ( As it is used as a power source for batteries such as P-HEV), the need for development of secondary batteries is increasing.

Currently commercialized secondary batteries include nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and lithium secondary batteries. Among these, lithium secondary batteries have the advantages of being able to charge and discharge freely, have a low self-discharge rate, and have high energy density. It's in the spotlight.

Lithium secondary batteries are classified into cylindrical, prismatic, or pouch types depending on the shape of the exterior material in which the electrode assembly is housed. Depending on the shape of the electrode assembly, they are a long sheet-shaped battery coated with active material and a jelly roll type wound with a separator between the positive and negative electrodes. , are roughly classified into a stacked type in which a plurality of anodes and cathodes of a predetermined size are sequentially stacked with a separator interposed between them, and a stacked/folded type in which stacked unit cells are wound with a long length of separator film. Among them, the jelly roll-type electrode assembly is the easiest to manufacture and has the advantage of high energy density per weight.

This jelly roll-type electrode assembly is manufactured by interposing a separator between the anode and the cathode and then winding it into a cylindrical shape. This winding process involves winding the separator and electrode using a two-part core and then winding the core from the electrode assembly. This is done by removing

Figure 1 is a perspective view of a conventional jelly roll-type electrode assembly. Figure 2 is an enlarged view of the 'U' portion of Figure 1. Figure 3 is a diagram for explaining changes in the length of electrodes in a conventional electrode assembly. Here, the partially enlarged view of FIG. 2 is a view showing the deformation of the center C after charging and discharging of the electrode assembly.

Referring to Figures 1 to 3, a conventional jelly roll-type electrode assembly may be formed by winding the positive electrode 10 and the negative electrode 20. The positive electrode tab 11 attached to the positive electrode 10 and the negative electrode tab 21 attached to the negative electrode 20 may protrude in opposite directions in the jelly roll-type electrode assembly. In the jelly roll-type electrode assembly, a separator is interposed between the anode 10 and the cathode 20.

The anode 10 may have a free edge. When the positive electrode tab 11 is not located at the distal end of the positive electrode sheet, one end of the positive electrode 10 may be provided with a coating layer coated with an active material, which may be referred to as a free-edge portion 10A. there is. A step may be formed around the center (C) of the electrode assembly by the free-edge portion (10A), and as the electrode assembly expands or contracts during the charging and discharging process of the battery cell, the electrode assembly may expand or contract as shown in the partially enlarged view of FIG. 2. The area around the center (C) may be deformed.

More specifically, referring to FIG. 3, the electrode length may change as the electrode assembly expands or contracts during the charging and discharging process of the battery cell. In this process, slipping may be limited depending on the friction between the electrodes 10 and 20 and the separator 30, and an impingement may occur in the cathode 20 facing the free edge portion 10A due to a step, etc. You can. If this phenomenon is repeated, the separator 30 between the anode 10 and the cathode 20 may be damaged, cracks may occur, or internal disconnection of the electrode assembly may occur, which greatly reduces the safety of the battery cell. there is.

The problem to be solved by the present invention is to provide an electrode assembly that improves the problem of internal disconnection of the electrode assembly due to changes in the length of the electrode when charging the battery cell, a battery cell including the same, and a cylindrical battery.

However, the problems to be solved by the embodiments of the present invention are not limited to the above-mentioned problems and can be expanded in various ways within the scope of the technical idea included in the present invention.

A jelly roll-type electrode assembly according to an embodiment of the present invention is a jelly roll-type electrode assembly including a positive electrode sheet, a negative electrode sheet, and a separator sheet interposed between the positive electrode sheet and the negative electrode sheet, and is located inside the jelly roll-type electrode assembly. The separator sheet portion facing one end of the anode sheet includes a first separator sheet portion facing the cathode sheet and a second separator sheet portion facing the anode sheet, and the first separator sheet portion and the cathode sheet. The coefficient of friction between the sheets is smaller than the coefficient of friction between the second separator sheet portion and the anode sheet.

One end portion of the positive electrode sheet may be formed as a pre-edge portion containing an active material.

The pre-edge portion may include a portion where one end of the positive electrode sheet is coated with a positive active material on the electrode current collector.

One end of the negative electrode sheet may be located inside the jelly roll-type electrode assembly than one end of the positive electrode sheet.

The jelly roll-type electrode assembly further includes a slip layer located between the first separator sheet portion and the cathode sheet, and a coefficient of friction between the slip layer and the first separator sheet portion or between the slip layer and the cathode sheet. The coefficient of friction may be smaller than the coefficient of friction between the second separator sheet portion and the anode sheet.

One end of the positive electrode sheet is formed as a pre-edge portion containing an active material, and the slip layer may be located on the first separator sheet portion covering the pre-edge portion.

Based on the cross section of the jelly roll-type electrode assembly, the free-edge portion may be located between both ends of the slip layer.

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

The slip layer may be made of a porous material.

The jelly roll-type electrode assembly may further include a barrier layer positioned between the separator sheet and the anode sheet to face the pre-edge portion.

The barrier layer may be located on the second separator sheet portion covering the pre-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 anode sheet may be greater than the coefficient of friction between the first separator sheet portion and the cathode sheet.

The jelly roll-type electrode assembly may further include a separator overlapping portion formed on a portion of the separator sheet that overlaps one end portion of the positive electrode sheet in a direction from the outside to the inside of the jelly roll-type electrode assembly.

The separator overlapping portion is formed between one end of the positive electrode sheet and the negative electrode sheet, and the thickness of the separator overlapping portion may be thicker than the thickness of the portion of the separator sheet that does not face one end of the positive electrode sheet.

The separator sheet includes a first separator sheet located on one side of the anode sheet and a second separator sheet located on the other side of the anode sheet, and the separator overlapping portion is located at one end of the anode sheet. It may include one end portion of the first separator sheet formed by bending in the same direction at least twice to cover the cutting surface of the and one end portion of the second separator sheet overlapping with one end portion of the first separator sheet.

One end of the second separator sheet may be bent at least twice to include two layers.

A battery cell according to another embodiment of the present invention includes the jelly roll-type electrode assembly described above, and a battery case for storing the jelly roll-type electrode assembly.

A cylindrical battery according to another embodiment of the present invention includes the above-described battery cell.

According to embodiments, the electrode assembly of the present invention can prevent internal disconnection of the jelly roll-type electrode assembly and improve the safety of the battery cell by minimizing friction between the electrode and the separator.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

Figure 1 is a perspective view of a conventional jelly roll-type electrode assembly.
Figure 2 is an enlarged view of the 'U' portion of Figure 1.
Figure 3 is a diagram for explaining changes in the length of electrodes in a conventional electrode assembly.
Figure 4 is a perspective view of an electrode assembly according to an embodiment of the present invention.
Figure 5 is an exploded perspective view showing the electrode assembly of Figure 4 before being wound.
Figure 6 is a diagram showing the electrode and separator located around the pre-edge portion.
FIG. 7 is a diagram showing a modified example of the electrode assembly of FIG. 6.
FIG. 8 is a diagram showing another modified example of the electrode assembly of FIG. 6.
Figure 9 is a diagram showing an electrode assembly according to another embodiment of the present invention.
Figure 10 is a diagram showing an electrode assembly according to another embodiment of the present invention.

Hereinafter, with reference to the attached drawings, various embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. The present invention may be implemented in many different forms other than those described below, and the scope of the present invention is not limited by the embodiments described herein.

In order to clearly explain the present invention, parts that are not relevant to the description are omitted, and identical or similar components are given the same reference numerals throughout the specification.

In addition, since the size and thickness of each component shown in the drawings are arbitrarily enlarged or reduced for convenience of explanation, it is obvious that the content of the present invention is not limited to what is shown. In the drawings below, the thickness of each layer is enlarged to clearly express the various layers and regions. In the drawings below, the thicknesses of some layers and regions are exaggerated for convenience of explanation.

Additionally, when a part of a layer, membrane, area, plate, etc. is described as being “on” or “on” another part, this means that the corresponding part of the layer, membrane, area, plate, etc. is “directly above” the other part. In addition, it should be interpreted to include cases where there is another part in between. Conversely, when a part of a corresponding layer, membrane, region, plate, etc. is described as being "right on top" of another part, it may mean that there are no other parts in between. In addition, being "on" or "on" a reference part means being located above or below the reference part, and necessarily meaning being located "above" or "on" the direction opposite to gravity. Maybe not. Meanwhile, just as describing something as being “above” or “on” another part, explaining it as being “below” or “under” another part may also be understood with reference to the above-described content.

In addition, throughout the specification, when a part is said to "include" a certain component, this means that it may further include other components rather than excluding other components, unless specifically stated to the contrary.

In addition, throughout the specification, when referring to “on a plane,” this means when the relevant part is viewed from above, and when referring to “in cross-section,” this means when a cross-section of the relevant part is cut vertically and viewed from the side.

Hereinafter, an electrode assembly according to an embodiment of the present invention will be described.

Figure 4 is a perspective view of an electrode assembly according to an embodiment of the present invention. Figure 5 is an exploded perspective view showing the electrode assembly of Figure 4 before being wound.

Referring to Figures 4 and 5, the jelly roll-type electrode assembly 50 of this embodiment includes a positive electrode sheet 100, a negative electrode sheet 200, and a separator sheet interposed between the positive electrode sheet 100 and the negative electrode sheet 200. 300). The anode sheet 100, the cathode sheet 200, and the separator sheet 300 may be alternately stacked to form a sheet-shaped laminate. The sheet-like laminate can be wound by a long rod-shaped core. Here, the positive electrode sheet 100 and the negative electrode sheet 200 may be collectively referred to as electrode sheets 100 and 200.

Meanwhile, at the center C of the jelly roll-type electrode assembly 50, the negative electrode sheet 200 may be wound to extend beyond the positive electrode sheet 100. That is, after the negative electrode sheet 200 and the separator sheet 300 are first wound around the core, the positive electrode sheet 100 may be additionally provided thereto and wound together. Considering the chemical reaction of a lithium ion battery, since the negative electrode receives lithium ions from the positive electrode, it may be desirable for the length and width of the negative electrode sheet 200 to be larger than the positive electrode sheet 100 for smooth charging and discharging. Therefore, when winding the sheet-shaped laminate, it may be preferable that the negative electrode sheet 200 is wound before the positive electrode sheet 100. Accordingly, the negative electrode sheet 200 is located on the innermost side of the center C, and the positive electrode sheet 200 is located on the innermost side of the center C. One end of (100) may be located outside the cathode sheet 200 (left side in FIG. 6). In other words, one end of the negative electrode sheet 200 may be located closer to the center C of the electrode assembly 50 than one end of the positive electrode sheet 100. The center C of the electrode assembly 50 may be inside as shown in FIG. 6 .

One end of the negative electrode sheet 200 may be located inside the center C of the electrode assembly 50 rather than one end of the positive electrode sheet 100. Additionally, the other end of the negative electrode sheet 200 located on the outer peripheral surface of the electrode assembly 50 may also be extended to cover the other end of the positive electrode sheet 100. Here, the center C of the electrode assembly 50 may refer to the radial center portion based on the cross section of the jelly roll-type electrode assembly.

The electrode sheets 100 and 200 may be formed by applying a slurry containing an electrode active material onto a current collector. The positive electrode sheet 100 may include a coated portion 130 to which the slurry is applied and an uncoated portion 120 to which the slurry is not applied, and the negative electrode sheet 200 may include a coating portion 230 to which the slurry is applied and the slurry to which the slurry is applied. It may include an uncoated area 220 that is not coated. In addition, the positive electrode tab 110 may be located on the uncoated portion 120 of the positive electrode sheet 100, and the negative electrode tab 210 may be located on the uncoated portion 220 of the negative electrode sheet 200. The anode tab 110 and the cathode tab 210 may protrude in directions opposite to each other in the height direction of the electrode assembly (x-axis direction in FIG. 5). However, it is also possible to be formed differently depending on the design.

Here, the electrode slurry may typically include an electrode active material, a conductive material, a binder, and a solvent, but is not limited thereto. Also, 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 films, sheets, foils, nets, porous materials, foams, and non-woven fabrics. Examples of the current collector used in the positive electrode sheet 110 include aluminum or an alloy thereof, and examples of the current collector used in the negative electrode sheet 200 include copper, nickel, stainless steel, or an alloy thereof. You can.

The separator sheet 300 may separate the anode sheet 100 and the cathode sheet 200 and provide a path for ions to move between the anode sheet 100 and the cathode sheet 200. The separator sheet 300 is a major component that determines the performance of secondary batteries. In order for the separator sheet 300 to have physical properties suitable for secondary batteries, physical properties such as minimizing thickness to lower electrical resistance and maximizing porosity and pore size are required. The characteristics must be satisfied. In addition, electrochemical properties such as wetting with the electrolyte must also be satisfied.

A coating layer may be formed by applying a coating material to one or both sides of the separator sheet 300, and the heat resistance and safety of the separator sheet 300 may be improved by the coating layer. For example, one or both sides of the fabric of the separator sheet 300 may be coated with a coating material containing alumina (Al- ₃ O- ₂ ) and a binder. When the fabric is coated with highly heat-resistant alumina, the separator sheet 300 can prevent internal short circuit of the battery cell by physically continuously blocking the contact between the anode and the cathode even in high temperature situations inside the battery cell, such as thermal runaway.

The coating layer of the separator sheet 300 may include ceramic particles and a polymer binder. An example of a ceramic particle may be alumina, and the characteristics of the separator sheet 300 may vary depending on the diameter of the alumina. For example, the smaller the diameter of alumina, the lower the coefficient of friction of the coating layer. As the diameter of alumina becomes smaller, the surface area of the particles increases, and a relatively large number of particles can contact the fabric of the separator sheet 300, so the adhesion of the particles improves and deformation of the separator sheet 300 can be suppressed. . In addition, even when the coating material is repeatedly applied on the fabric of the separator sheet 300, if the particle diameter is small, the thickness of the coating layer may become thin, so the air permeability of the coating layer increases compared to the case where the particle diameter is large, The ion conduction resistance of the separator sheet 300 may be lowered.

It may vary depending on the coating material forming the coating layer, but when forming the coating layer using a coating material with a higher coefficient of friction compared to the separator fabric, the coating layer may be formed on one side of the separator sheet 300 facing the anode sheet 100. You can. Alternatively, coating layers may be formed on both sides of the separator sheet 300, and in this case, the friction coefficient of the first coating layer formed on one side of the separator sheet 300 facing the cathode sheet 200 is that of the anode sheet 100. It can be designed to be smaller than the friction coefficient of the second coating layer formed on the other side of the separator sheet 300 facing the surface. In order to make the friction coefficients of the first coating layer and the second coating layer different from each other, it is possible to adjust the diameter of the ceramic particles as described above.

Meanwhile, one end of the positive electrode sheet 100 may have a pre-edge portion 100A. One end of the positive electrode sheet 100 may be formed of a coated portion 130 rather than an uncoated portion 120, and this distal portion may be referred to as a pre-edge portion or a coated-edge portion. As shown in FIG. 5, according to this embodiment, the positive electrode tab 110 may not be located at one end of the positive electrode sheet 100, but may be located at the center. Therefore, the pre-edge portion 100A means that the positive electrode tab 110 is not positioned at one end of the positive electrode sheet 100 or the uncoated region 120 for positioning the positive electrode tab 110 is not formed. It can be referred to as . Alternatively, one end of the positive electrode sheet 100 is formed as a coating portion 130 and the coating layer is cut, so it may be referred to as a coating-edge portion. Here, one end of the positive electrode sheet 100 on which the pre-edge portion or the coating-edge portion is formed may be the core of a jelly roll-type electrode assembly. Accordingly, the anode tab 110 may not be located around the center C of the electrode assembly.

In this way, the free-edge portion 100A is formed at one end of the positive electrode sheet 100, so that when the volume of the electrode assembly expands, the part of the negative electrode sheet 200 facing the free-edge portion 100A is bent. This may cause damage to the separator sheet 300. However, in the electrode assembly of this embodiment, the above-mentioned problem can be solved by changing the level of friction between the separator sheet 300 and the electrode sheets 100 and 200.

Figure 6 is a diagram showing the electrode and separator located around the pre-edge portion described above. FIG. 7 is a diagram showing a modified example of the electrode assembly of FIG. 6. FIG. 8 is a diagram showing another modified example of the electrode assembly of FIG. 6.

In the electrode assembly of the present embodiment according to FIG. 6, the electrode sheets 100, 200 and the separator sheet 300 around the pre-edge portion 100A are wound, but in FIG. 6, they are shown flat for convenience of explanation, and the electrode The sheets 100 and 200 and the separator sheet 300 are shown in a state where they are not in close contact with each other. In FIG. 6 , the negative electrode sheet 200 disposed above and below the positive electrode sheet 100 may be wound before or after the positive electrode sheet 100 when the electrode assembly is wound.

Referring to FIG. 6, in the electrode assembly of this embodiment, the separator sheet 300 is a separator facing the pre-edge portion 100A corresponding to one end of the positive electrode sheet 100 located inside the jelly roll-type electrode assembly. It may have a sheet portion. Here, facing the pre-edge portion 100A may mean overlapping each other in the direction toward the center C of the jelly roll-type electrode assembly 50 of FIG. 4. In other words, the separator sheet portion overlapping the free-edge portion 100A in the z-axis direction in FIGS. 5 and 6 is the first separator sheet portion facing the cathode sheet 200 and the separator sheet portion facing the anode sheet 100. It may include a second separator sheet portion.

The anode tab (110 shown in FIG. 5) according to this embodiment is formed at a position away from the center C of the electrode assembly 50 shown in FIG. 4 (see FIG. 5). The center C of the electrode assembly may be located on one side of the y-axis direction where the free edge portion 100A is located in FIGS. 5 and 6. Accordingly, the coating portion 130 of FIG. 5 is formed on the current collector of the positive electrode sheet 100 up to one end of the positive electrode sheet 100 adjacent to the center C of the electrode assembly, and the pre-edge portion 100A is It may refer to a portion at one end of the positive electrode sheet 100 where the coating portion 130 is formed on the current collector of the positive electrode sheet 100. In other words, one end of the pre-edge portion 100A may have the coating portion 130 cut.

The separator sheet portion corresponding to the pre-edge portion 100A may have a width of the first range T1 based on one end edge of the anode sheet 100. The separator sheet 300 may include a first surface 300A facing the negative electrode sheet 200 and a second surface 300B facing the positive electrode sheet 100. The separator sheet 300 portion may include a first separator sheet portion facing the anode sheet 200 and a second separator sheet portion facing the anode sheet 100. The first separator sheet part may include a first surface (300A), and the second separator sheet part may include a second surface (300B).

In this embodiment, the coefficient of friction between the first surface 300A of the first separator sheet part and the anode sheet 200 is different from the coefficient of friction between the second surface 300B of the second separator sheet part and the anode sheet 100. can do. Specifically, the coefficient of friction between the first surface 300A of the first separator sheet part and the anode sheet 200 may be smaller than the coefficient of friction between the second surface 300B of the second separator sheet part and the anode sheet 100. . In this way, by forming a relatively small friction coefficient between the first separator sheet portion having the first surface 300A of the separator sheet 300 located around the pre-edge portion 100A and the cathode sheet 200, the separator The sheet 300 and the negative electrode sheet 200 may slip, and the bending phenomenon of the negative electrode sheet 200 and the resulting internal disconnection of the electrode assembly can be prevented. That is, the negative electrode sheet 200 can slide better than the positive electrode sheet 100 when the electrode assembly is expanded. Therefore, when the electrode assembly expands as the battery cell is charged and the length of the electrode sheet increases, it is possible to prevent the end of the negative electrode sheet 200 from bending.

In this embodiment, the relative friction coefficient is adjusted differently, and it is possible to compare the magnitude of the friction coefficient described above through a conventional friction coefficient measurement method and friction coefficient measurement equipment.

The separator sheet 300 may be provided in various ways.

As described above, in order to realize a relatively small coefficient of friction between the first separator sheet portion having the first surface 300A of the separator sheet 300 located around the pre-edge portion 100A and the cathode sheet 200. It is also possible to adjust the surface roughness. As an example, coating layers may be formed on both sides of the separator sheet 300, respectively. The surface roughness of the first surface 300A and the second surface 300B may be formed differently depending on the coating layer formed on each surface. When the coating layer includes ceramic particles, the diameters of 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 be different from each other. 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, a coating layer is formed only on one side of the separator sheet 300, so that the first side 300A and the second side 300B may have different surface roughness. When the surface roughness of the coating layer is smaller than that of the fabric of the separator sheet 300, the coating layer may be formed on the first side 300A. When the surface roughness of the coating layer is greater than that of the fabric of the separator sheet 300, the coating layer may be formed on the second surface 300B.

As another example, a coating layer may not be formed on the separator sheet 300. The surface roughness of the first side 300A and the second side 300B of the separator sheet 300 may vary depending on the characteristics of the separator fabric. At this time, the first side 300A may be a side of the separator fabric with a relatively low surface roughness, and the second side 300B may be a side of the separator fabric with a relatively high surface roughness.

In this embodiment, the relative surface roughness is adjusted differently, and it is possible to compare the size of the surface roughness described above through conventional surface roughness measurement methods and surface roughness measurement equipment.

Referring to FIG. 7, a slip layer 400 may be provided in the electrode assembly according to another embodiment of the present embodiment.

The slip layer 400 is provided between the first separator sheet portion, which is the separator sheet 300, around the free-edge portion 100A and the cathode sheet 200, thereby preventing slippage between the separator sheet 300 and the cathode sheet 200. This may lead to . The slip layer 400 may have a lower coefficient of friction than the separator sheet 300. Specifically, the friction coefficient between the slip layer 400 and the first separator sheet portion or the friction coefficient between the slip layer 400 and the anode sheet 200 is the coefficient of friction between the second separator sheet portion and the anode sheet 100. It may be smaller than the friction coefficient of . The slip layer 400 can be attached to the anode sheet 200 or the first separator sheet using a material that is adhesive at room temperature. When the slip layer 400 is attached to the anode sheet 200, the friction coefficient between the slip layer 400 and the first separator sheet portion is the friction coefficient between the second separator sheet portion and the anode sheet 100. It may be smaller than, and when the slip layer 400 is attached to the first separator sheet portion, the coefficient of friction between the slip layer 400 and the cathode sheet 200 is the second separator sheet portion and the anode sheet ( 100) may be smaller than the coefficient of friction between

The slip layer 400 may be made of a porous material. Since the slip layer 400 includes a plurality of pores, it may not impede the movement of lithium ions or charges between the positive electrode sheet 100 and the negative electrode sheet 200. If the slip layer 400 is not made of a porous material, short circuit problems due to lithium precipitates may occur. Examples of materials that can be used in the slip layer 400 include polyethylene (PE) or polypropylene (PP), and the material used in the fabric of the separator sheet 300 is applied to the slip layer 400. It is also possible. Alternatively, the slip layer 400 may be used to have a ceramic coating on the fabric surface of the separator sheet 300.

The slip layer 400 may be provided around the free-edge portion 100A. The slip layer 400 may be positioned to correspond to the free-edge portion 100A. Here, corresponding to the pre-edge portion 100A may mean overlapping each other in the direction toward the center C of the jelly roll-type electrode assembly.

The slip layer 400 may be located on the first surface 300A of the separator sheet 300 covering the free-edge portion 100A, which is not in contact with the free-edge portion 100A.

Since the positive electrode sheet 100 repeats expansion or contraction according to charging and discharging of the battery cell including the electrode assembly, the slip layer 400 may be provided in consideration of the fluctuating position of the free-edge portion 100A. Specifically, as shown in FIG. 7, the position of the free edge portion 100A may change within the first range T1 according to expansion or contraction of the positive electrode sheet 100. At this time, the first length L1, which is the length of the slip layer 400, is provided larger than the length of the first range T1, so that the slip layer 400 and the free-edge portion 100A correspond to each other. . In the direction in which the anode sheet 100, the cathode sheet 200, or the separator sheet 300 extends, when the part that is wound first is defined as the inside and the part that is wound later is defined as the outside, one end of the slip layer 400 may be located inside the free-edge portion 100A, and the other end of the slip layer 400 may be located outside the free-edge portion 100A. In the direction in which the anode sheet 100, the cathode sheet 200, or the separator sheet 300 extends, the slip layer 400 is arranged so that the pre-edge portion 100A is located between both ends of the slip layer 400. It can be. Based on the cross section of the wound electrode assembly, the slip layer 400 may be arranged so that the free-edge portion 100A is located between both ends of the slip layer 400. At this time, the cross section of the wound electrode assembly points to the plane shown in FIG. 6 and may be a plane perpendicular to the central axis around which the electrode assembly is wound. Here, both ends of the slip layer 400 may be ends in the longitudinal direction, and the longitudinal direction may be a direction in which the anode sheet 100, the cathode sheet 200, or the separator sheet 300 extends.

For a specific example, the first length L1 of the slip layer 400 may range from 10 mm to 30 mm, or 15 mm to 25 mm, or the first length L1 of the slip layer 400 may be about 20 mm. You can. Here, the first length L1 may be calculated based on the direction in which the anode sheet 100, the cathode sheet 200, or the separator sheet 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, the barrier layer 400' according to the present embodiment is provided between the separator sheet 300 and the cathode sheet 200 in the embodiment of FIG. 7, and is provided between the anode sheet 100 and the separator. It is also possible to provide it between the sheets 300. The barrier layer 400' is positioned to correspond to the free-edge portion 100A and may be located on the second separator sheet portion 300 covering the free-edge portion 100A. At this time, the barrier layer 400' not only induces slippage between the separator sheet 300 and the anode sheet 100, but also acts as a barrier layer between the cathode sheet 200 and the anode sheet 100. (400') is doubled to physically prevent internal short circuit. 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 anode sheet 100 is the coefficient of friction between the first separator sheet portion and the cathode sheet 200. It is preferable that it is greater than the coefficient of friction between them. This is because, although it is possible to prevent internal short circuits between the cathode sheet 200 and the anode sheet 100 through the barrier layer 400', it also prevents the bending phenomenon of the cathode sheet 200, thereby greatly increasing the effect of preventing internal short circuits. You can.

In FIG. 8, only the barrier layer 400' is provided between the anode sheet 100 and the separator sheet 300. However, as a modified example, the cathode sheet 200 and the separator sheet are provided as described in FIG. 7. A barrier layer 400' between the anode sheet 100 and the separator sheet 300 may also be provided along with a slip layer 400 between 300.

Figure 9 is a diagram showing an electrode assembly according to another embodiment of the present invention.

Referring to FIG. 9, at least one of the two slip layers 400 described in FIG. 7 may be omitted, and a separator overlapping portion 305P may be formed at the location where the slip layer 400 is omitted. The separator overlapping portion 305P may be formed in a portion of the separator sheet 300 that overlaps one end portion of the positive electrode sheet 100 in a direction from the outside to the inside (center portion) of the jelly roll-type electrode assembly. The separator overlapping portion 305P according to this embodiment is formed between one end of the positive electrode sheet 100 and the negative electrode sheet 200, and at this time, the thickness of the separator overlapping portion 305P is at one end of the positive electrode sheet 100. It can be formed thick compared to the thickness of the portion of the separator sheet that does not face each other.

The separator sheet 305 according to this embodiment includes a first separator sheet 305a located on one side of the anode sheet 100 and a second separator sheet 305b located on the other side of the anode sheet 100. can do. The separator overlapping portion 305P is a portion of the first separator sheet 305a formed by bending the first separator sheet 305a in the same direction at least twice so as to cover the cutting surface 100C of one end of the anode sheet 100. It may include an end portion and an end portion of the second separator sheet 305b that overlaps an end portion of the first separator sheet 305a. Here, one end of the first separator sheet 305a may be bent to cover the pre-edge portion 100A. One end of the first separator sheet 305a may be bent twice and cover the top, side, and bottom surfaces of the free-edge portion 100A.

One end of the second separator sheet 305b may be bent at least twice to include two layers. Specifically, the second separator sheet 305b may be bent in a direction toward the first separator sheet 305a and bent again to overlap the bent portion of the first separator sheet 305a. One end portion of the second separator sheet 305b may include two layers. According to this embodiment, a triple-overlapping separator overlap portion 305P is formed between the positive electrode sheet 100 and the negative electrode sheet 200, thereby physically preventing an internal short between the negative electrode sheet 200 and the positive electrode sheet 100. This can be prevented.

Additionally, the slip layer 400 according to this embodiment may include a separator base layer 400a and an adhesive layer 400b formed on one surface of the separator base layer 400a. The adhesive layer 400b may serve to attach the slip layer 400 to the negative electrode sheet 200. The slip layer 400 may further include a back coating layer 400c located on the back of the separator base layer 400a where the adhesive layer 400b is located. The back coating layer 400c serves to prevent the adhesive layer 400b from adhering to each other when the slip layer 400 is wound in the form of a tape in the preparation process for attaching the slip layer 400 to the anode sheet 200. can do.

The description of the slip layer 400 described here can be applied to the slip layer 400 previously described in FIGS. 4 to 7.

Figure 10 is a diagram showing an electrode assembly according to another embodiment of the present invention.

The embodiment of FIG. 10 is mostly the same as the embodiment described in FIG. 9, but differences will be described below.

Referring to FIG. 10 , the second separator sheet 305c may not be bent, unlike the second separator sheet 305b described in FIG. 9 . In other words, the second separator sheet 305c according to this embodiment may overlap the first separator sheet 305a of FIG. 9 without bending one end. Therefore, the separator overlap portion 305P according to the present embodiment is formed by forming a double-overlapping separator overlap portion 305P between the anode sheet 100 and the cathode sheet 200, thereby forming the anode sheet 200 and the anode sheet ( 100) Internal short circuits can be physically prevented.

In addition to the differences described above, all of the information described in FIG. 9 is applicable to this embodiment.

Meanwhile, the jelly roll-type electrode assembly according to this embodiment described above can be stored in a battery case to form a battery cell. Specifically, the jelly roll-type electrode assembly can be manufactured into a battery cell by inserting it into a cylindrical or square metal container, filling it with an electrolyte solution, and sealing the metal container. The battery cell including the jelly roll-type electrode assembly may be a cylindrical battery or a prismatic battery, but the shape of the battery cell including the jelly roll-type electrode assembly is not limited to the examples described above.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims are also possible. It falls within the scope of invention rights.

100: anode sheet
100A: Pre-edge part
110: anode tab
120: Mujibu
130: Coating part
200: cathode sheet
300: Separator sheet
305: Separator overlap portion
400: slip layer
400': barrier layer

Claims (18)

A jelly roll-type electrode assembly comprising an anode sheet, a cathode sheet, and a separator sheet interposed between the anode sheet and the cathode sheet,
The separator sheet portion facing one end of the anode sheet located inside the jelly roll-type electrode assembly includes a first separator sheet portion facing the cathode sheet and a second separator sheet portion facing the anode sheet. ,
A jelly roll type electrode assembly wherein the coefficient of friction between the first separator sheet portion and the anode sheet is smaller than the coefficient of friction between the second separator sheet portion and the anode sheet. In paragraph 1:
A jelly roll-type electrode assembly in which one end of the positive electrode sheet is formed as a free-edge portion containing an active material. In paragraph 2,
The pre-edge portion is an electrode assembly including a portion where one end of the positive electrode sheet is coated with a positive active material on an electrode current collector. In paragraph 1:
A jelly roll-type electrode assembly wherein one end of the negative electrode sheet is located inside the jelly roll-type electrode assembly than one end of the positive electrode sheet. In paragraph 1:
It further includes a slip layer located between the first separator sheet portion and the cathode sheet,
A jelly roll type electrode assembly wherein the coefficient of friction between the slip layer and the first separator sheet portion or the coefficient of friction between the slip layer and the cathode sheet is smaller than the coefficient of friction between the second separator sheet portion and the anode sheet. In paragraph 5,
One end portion of the positive electrode sheet is formed as a pre-edge portion containing an active material,
The slip layer is a jelly roll-type electrode assembly located on the first separator sheet portion covering the pre-edge portion. In paragraph 6:
Based on the cross section of the jelly roll type electrode assembly, the free-edge portion is located between both ends of the slip layer. In paragraph 5,
A jelly roll-type electrode assembly wherein the slip layer has a length of 10 mm to 30 mm. In paragraph 5,
A jelly roll-type electrode assembly in which the slip layer is made of a porous material. In paragraph 1:
A jelly roll-type electrode assembly further comprising a barrier layer positioned between the separator sheet and the anode sheet to face the free-edge portion. In paragraph 10:
The barrier layer is a jelly roll-type electrode assembly located on the second separator sheet portion covering the pre-edge portion. In paragraph 11:
A jelly roll type electrode assembly 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 anode sheet is greater than the coefficient of friction between the first separator sheet portion and the cathode sheet. In paragraph 1:
A jelly roll-type electrode assembly further comprising a separator overlapping portion formed on a portion of the separator sheet that overlaps one end portion of the positive electrode sheet in a direction from the outside to the inside of the jelly roll-type electrode assembly. In paragraph 13:
The separator overlapping portion is formed between one end of the positive electrode sheet and the negative electrode sheet, and the thickness of the separator overlapping portion is thicker than the thickness of the portion of the separator sheet that does not face one end of the positive electrode sheet. Electrode assembly. In paragraph 14:
The separator sheet includes a first separator sheet located on one side of the positive electrode sheet and a second separator sheet located on the other side of the positive electrode sheet,
The separator overlapping portion includes one end portion of the first separator sheet formed by bending the first separator sheet in the same direction at least twice to cover the cut surface of one end portion of the positive electrode sheet, and one end portion of the first separator sheet A jelly roll-type electrode assembly including one end portion of the second separator sheet that overlaps. In paragraph 15:
A jelly roll-type electrode assembly wherein one end of the second separator sheet is bent at least twice and includes two layers. A jelly roll-type electrode assembly according to claim 1, and
A battery cell including a battery case accommodating the jelly roll-type electrode assembly. A cylindrical battery comprising the battery cell according to claim 17.