KR20230014076A - Jelly roll type electrode assembly and method of manufacturing the same - Google Patents

Abstract

A jelly-roll type electrode assembly according to an embodiment of the present invention is a jelly-roll type electrode assembly in which a sheet-type stack including an electrode and a separator is wound, wherein the separator includes a double-sided coating layer, the coating layer includes a mixture of first alumina and second alumina, the second alumina is included in 16 to 40 parts by weight with respect to 100 parts by weight of the mixture, and the particle diameter of the first alumina is smaller than that of the second alumina.

Description

Jelly-roll type electrode assembly and manufacturing method thereof

Cross-citation with related application(s)

This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0094709 dated July 20, 2021, and all contents disclosed in the literature of the Korean patent application are incorporated as part of this specification.

The present invention relates to a jelly-roll type electrode assembly and a method for manufacturing the same, and more particularly, to a jelly-roll type electrode assembly with improved safety and high process yield and a method for manufacturing the same.

As the use of portable devices such as mobile phones, laptop computers, camcorders, and digital cameras has become commonplace in modern society, development of technologies in fields related to the above mobile devices has become active. In addition, a secondary battery capable of charging and discharging is a method for solving air pollution such as existing gasoline vehicles using fossil fuels, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles ( P-HEV), etc., 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. It is getting popular.

Depending on the shape of the battery case, secondary batteries are classified into cylindrical batteries and prismatic batteries in which the electrode assembly is embedded in a cylindrical or prismatic metal can, and pouch-type batteries in which the electrode assembly is embedded in a pouch-type case made of an aluminum laminate sheet. .

Secondary batteries are also classified according to the structure of an electrode assembly having a laminated structure of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. Representatively, a jelly-roll type (wound type) electrode assembly having a structure in which long sheet-type positive and negative electrodes are wound with a separator interposed therebetween, a plurality of positive and negative electrodes cut in units of a predetermined size with a separator interposed therebetween and stacked (stacked) electrode assemblies sequentially stacked. Recently, in order to solve the problems of the jelly-roll type electrode assembly and the stack type electrode assembly, a stack/folding type electrode assembly, which is a mixture of the jelly-roll type and stack type, has been developed. Among them, the jelly-roll type electrode assembly is the easiest to manufacture and has a high energy density per weight.

Separation membrane isolates two electrodes (anode/cathode) in a secondary battery to block electrical short-circuit caused by physical contact, and provides a passage through which ions can move between the two electrodes through an electrolyte solution supported in micropores so as to have ionic conductivity. It is a film material with the function of In the case of a secondary battery for an electric vehicle, unlike conventional small electronic devices, heat resistance characteristics are required to secure the safety of the battery even in an environment exposed to heat of about 150 ° C. Accordingly, polypropylene (PP), which has excellent thermal properties, has recently been used as a material for separators, and a ceramic coated SRS (safety reinforced separator) separator with improved heat resistance by coating ceramic particles and a polymer binder on one side or both sides of the separator has been developed. It is applied to secondary batteries.

On the other hand, in applying the double-sided SRS separator to the jelly-roll type electrode assembly, there is a problem that the process yield is somewhat lowered due to the surface roughness value of the SRS separator and the winding core or the frictional force between the SRS separator and the winding core accordingly. Specifically, when a double-sided SRS separator is applied, a slip phenomenon or a tail loss phenomenon may occur when the core is removed depending on the frictional force of the coating layer formed on the separator or the difference between the frictional force between the core and the separator, and accordingly, the fairness of the jelly-roll type electrode assembly is improved. It was difficult to secure.

Therefore, in order to solve these problems of the prior art, there is a need for a jelly-roll type electrode assembly and a method of manufacturing the same in consideration of the surface roughness values of the SRS separator and the winding core.

The problem to be solved by the present invention is to provide a jelly-roll type electrode assembly and a method for manufacturing the same with improved safety and high process yield.

However, the problems to be solved by the embodiments of the present invention are not limited to the above problems and can be variously extended within the scope of the technical idea included in the present invention.

In the jelly-roll type electrode assembly in which a sheet-type laminate including an electrode and a separator is wound according to an embodiment of the present invention, the separator includes a double-sided coating layer, and the coating layer includes a mixture of first alumina and second alumina, , The surface roughness (Ra) of the separator may be 500 nm to 1 μm, and a particle diameter of the first alumina may be smaller than a particle diameter of the second alumina.

Based on 100 parts by weight of the mixture, the second alumina may be included in 16 to 40 parts by weight.

Based on 100 parts by weight of the mixture, the first alumina may be included in 60 to 84 parts by weight.

The particle diameter of the first alumina may be 20 to 50 nm.

The particle diameter of the second alumina may be 300 to 500 nm.

The electrode assembly may be a double-sided SRS laminate in which a separator, an anode, a separator, and a cathode are sequentially stacked.

The length of the core of the jelly roll-type electrode assembly may be about 10 cm to 12 cm, and the radius may be about 4 cm to 5 cm.

A method for manufacturing a jelly-roll type electrode assembly according to an embodiment of the present invention includes providing a separator including a double-sided coating layer, calculating a difference in surface roughness between the separator and the winding core, and If the difference between the surface roughness values is less than the first value, the surface roughness of the winding core is adjusted using a first process, and when the difference between the surface roughness values of the separator and the winding core is greater than or equal to the first value, a second process is performed. adjusting the surface roughness of the winding core by using the winding core; and winding a sheet-like laminate including an electrode and the separator using the winding core having the adjusted surface roughness, wherein the coating layer comprises first alumina and It includes a mixture of second alumina, the surface roughness (Ra) of the separator is 500 nm to 1 μm, and the particle diameter of the first alumina may be smaller than the particle diameter of the second alumina.

Based on 100 parts by weight of the mixture, the second alumina may be included in 16 to 40 parts by weight.

Based on 100 parts by weight of the mixture, the first alumina may be included in 60 to 84 parts by weight.

The first value Rmax may be between 0.05s and 0.15s.

The first process may be a sanding process.

The second process may be a lapping process.

The sheet-like laminate is wound by a rod-shaped winding core, the winding core includes a first part and a second part separated around a rotation axis, and one end of the sheet-like laminate is the first part and the second part. It is fixed by being inserted into the slit between the second parts, and the size of the slit may be greater than 0.8 mm.

The sheet-like laminate is wound by a rod-shaped core, the surface roughness of the core is less than or equal to a second value, and the second value (Rmax) may be 0.15 s to 0.25 s.

When the second process is used in the step of adjusting the surface roughness of the winding core, the step of calculating the difference between the surface roughness of the separator and the winding core may be performed again.

If the difference in surface roughness calculated in the step of calculating the difference between the surface roughness of the separator and the winding core, which was performed again, is equal to or greater than the first value, the step of adjusting the surface roughness of the winding core is performed using a second process. It can be.

If the difference in surface roughness calculated in the step of calculating the difference between the surface roughness of the separator and the winding core is less than the first value, the step of adjusting the surface roughness of the winding core is performed using a first process. and winding the sheet-type laminate including the electrode and the separator using the winding core having the controlled surface roughness may be performed.

A battery cell according to another embodiment of the present invention includes the above-described jelly-roll type electrode assembly.

According to the embodiments, the jelly-roll type electrode assembly and method for manufacturing the same of the present invention include a double-sided SRS separator, thereby improving heat resistance and safety, and controlling the surface roughness of the SRS separator and the winding core, thereby improving process yield.

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.

1 is a perspective view showing a jelly-roll type electrode assembly according to an embodiment of the present invention.
2 is a flowchart of a method for manufacturing a jelly-roll type electrode assembly according to an embodiment of the present invention.
3 is a side view of a winding core used in a jelly-roll type electrode assembly manufacturing method according to an embodiment of the present invention.
4 is a cross-sectional view of a winding core used in a jelly-roll type electrode assembly manufacturing method according to an embodiment of the present invention.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out 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 describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar components 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 description, it is obvious that the contents of the present invention are not limited to those shown. In the following drawings, the thickness of each layer is shown enlarged in order to clearly express various layers and regions. Also, in the following drawings, for convenience of description, thicknesses of some layers and regions are exaggerated.

Also, when a portion of a layer, film, region, board, etc. is described as being "on" or "on" another portion, this means that the layer, film, region, board, etc. portion in question is "directly on" the other portion. In addition, it should be construed as including the case where there is another part in between. Conversely, when a part of a corresponding layer, film, region, plate, etc. is described as being "directly on" another part, it may mean that there is no other part in between. In addition, to be "on" or "on" a reference part means to be located above or below the reference part, and to necessarily be located "above" or "on" in the opposite direction of gravity does not mean It may not be. On the other hand, similar to the description of being "above" or "on" another part, the description of being "below" or "below" another part will also be understood with reference to the above-described content.

In addition, throughout the specification, when a certain part "includes" a certain component, it means that it may further include other components without excluding other components unless otherwise stated.

In addition, throughout the specification, when it is referred to as "planar", it means when the corresponding part is viewed from above, and when it is referred to as "cross-section", it means when the cross section of the corresponding part cut vertically is viewed from the side.

Hereinafter, a jelly-roll type electrode assembly according to an embodiment of the present invention will be described.

1 is a perspective view showing a jelly-roll type electrode assembly according to an embodiment of the present invention.

Referring to FIG. 1 , the jelly-roll type electrode assembly 100 of this embodiment may include a positive electrode 110, a negative electrode 120, and a separator 130 interposed between the positive electrode 110 and the negative electrode 120. . In FIG. 1, a separator 130, a positive electrode 110, a separator 130, and a negative electrode 120 are stacked in this order, and a jelly-roll type electrode assembly 100 is shown in which the positive electrode 110 is wound inside. However, this is not necessarily the case, and the separator 130, the negative electrode 120, the separator 130, and the positive electrode 110 may be stacked in order so that the negative electrode 120 is located inside. In addition, the positive electrode 110, the separator 130, the negative electrode 120, and the separator 130 are stacked in this order, or the negative electrode 120, the separator 130, the positive electrode 110, and the separator 130 are stacked in that order. It is also possible to become As such, the electrodes 110 and 120 and the separator 130 are alternately stacked to form a sheet-like stack, and the sheet-like stack may be wound by a long rod-shaped core.

The positive electrode 110 and the negative electrode 120 may be collectively referred to as electrodes 110 and 120 . The electrodes 110 and 120 may be obtained by applying a slurry containing an electrode active material on a current collector. Here, the electrode slurry may typically include an electrode active material, a conductive material, a binder, and a solvent, but is not limited thereto. In addition, the current collector may be made of stainless steel, aluminum, copper, nickel, titanium, calcined carbon, or the like, and may be provided in various forms such as a film, sheet, foil, net, porous material, foam, or non-woven fabric. Examples of the current collector used for the positive electrode 110 include aluminum or an alloy thereof, and examples of the current collector used for the negative electrode 120 include copper, nickel, stainless steel, or any one of these alloys. .

The separator 130 may separate the positive electrode 110 and the negative electrode 120 and provide a passage for ions moving between the positive electrode 110 and the negative electrode 120 . Separator 130 is a major component that determines the performance of a secondary battery. In order for the separator 130 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. must be satisfied In addition, electrochemical properties such as wettability with an electrolyte must also be satisfied.

On the other hand, as the secondary battery is used in medium and large-sized devices, as the temperature inside the battery cell rises to 150 ° C. or higher, the separator 130 melts, causing an internal short circuit of the battery cell. Therefore, since the separator 130 used in the secondary battery must satisfy heat resistance in addition to physical and electrochemical properties, attempts have been made to change the material of the separator 130 to polyolefin, polyethylene, polypropylene, or a composite thereof. Recently, in addition to simply changing the material, a method of manufacturing a separator 130 in which one or both sides of a porous substrate such as polyolefin, polyethylene, or polypropylene is coated with a coating material of ceramic material is mainly used. Such a separator 130 may be referred to as an SRS or an SRS separator, and details of the SRS separator may be described with reference to known literature.

A coating layer may be formed by applying a coating material to one side or both sides of the separation membrane 130 , and heat resistance and safety of the separation membrane 130 may be improved by the coating layer. For example, a coating material including alumina (Al ₃ O ₂ ) and a binder may be coated on one side or both sides of the fabric of the separator 130 . When the fabric is coated with alumina having strong heat resistance, the separator 130 physically continuously blocks contact between the positive electrode and the negative electrode even in a high-temperature situation inside the battery cell such as thermal runaway, thereby preventing an internal short circuit of the battery cell.

The separator 130 may be provided as a double-sided SRS separator. A coating layer may be formed by applying a coating material to both surfaces of the fabric of the separator 130 facing the electrodes 110 and 120 . When the coating layer is formed on both sides of the separation membrane 130, since either one side or the other side of the separation membrane 130 is in contact with the electrodes 110 and 120, the separation membrane 130 can be freely disposed in the process. In addition, simplification of the process and reduction of process time can be achieved accordingly.

The coating layer of the separator 130 may include ceramic particles and a polymer binder. An example of the ceramic particle is alumina, and the characteristics of the separator 130 may vary depending on the diameter of the alumina. For example, as the diameter of alumina decreases, the surface area of the particles increases, and since a relatively large number of particles can contact the original fabric of the separation membrane 130, the adhesion of the particles is improved and deformation of the separation membrane 130 is suppressed. can In addition, even when the coating material is repeatedly applied on the fabric of the separator 130, the thickness of the coating layer can be reduced if the particle diameter is small, so the air permeability of the coating layer increases compared to the case where the particle diameter is large, The ion conduction resistance of (130) can be lowered. In order to achieve the above effect, fine particles of alumina having a small diameter may be used as a material for the coating material, and their diameter may be 20 to 50 nm.

The coating layer of the separator 130 may be formed on both sides, and the surface roughness of the separator 130 may be determined by the coating layer. When the coating layer of the separator 130 is formed using fine particle alumina, the surface roughness of the coating layer may be low, and accordingly, a phenomenon (slip phenomenon) of the separator 130 may appear during the winding process. In addition, if the surface roughness of the coating layer is too large, the separator 130 may be cut or damaged during the winding process. In addition, depending on the surface roughness of the separation membrane 130, in the process of removing the winding core, the separation membrane 130 may be pulled out along the winding core or the separation membrane 130 may be damaged. Therefore, the surface roughness of the separator 130 applied to the jelly-roll electrode assembly 100 may need to be properly adjusted.

The surface roughness of the separator 130 may be adjusted by adjusting the particle size of alumina included in the coating material. For example, the coating material may include a mixture of fine particle alumina and general alumina. Since the surface roughness of the coating layer may vary depending on the ratio of fine alumina particles and normal alumina included in the mixture, a coating layer of an appropriate level required for the separator 130 may be formed by varying the ratio of the two particles. At this time, since the surface roughness of an appropriate level may vary depending on the difference in roughness with respect to the winding core, the width of the separator 130, or the size of the jelly-roll type electrode assembly, the appropriate mixture ratio may vary as each condition changes. there is. As will be described later, it may be desirable for the mixture to include normal alumina in a proportion of 40% or less. The mixture may preferably contain normal alumina in a proportion of at least 16%.

Here, normal alumina is for distinction from fine particle alumina, and may refer to alumina particles having a larger diameter than fine particle alumina. The diameter of normal alumina may be 300 to 500 nm. Further, for convenience, the fine particle alumina may be referred to as a first alumina, and the normal alumina may be referred to as a second alumina.

Hereinafter, a method for manufacturing a jelly-roll type electrode assembly according to an embodiment of the present invention will be described.

Since the length value of the separator 130 in the sheet-like laminate is greater than the length value of the electrodes 110 and 120, the winding core may contact one end of the separator 130 extending from one end of the electrodes 110 and 120 in the winding process. . Therefore, when the difference in surface roughness between the separator 130 and the winding core is large, a problem may occur that a part of the separator 130 is pulled out or the separator 130 is damaged when the winding core is discharged, and thus the electrode assembly 100 The yield of may be lowered.

As such, since the yield of the jelly-roll type electrode assembly 100 may be lowered depending on the difference in surface roughness of the separator 130 and the winding core, in addition to changing the surface roughness of the separator 130, it is necessary to adjust the surface roughness of the winding core. . Therefore, the manufacturing method according to the present embodiment may include a process of adjusting the surface roughness of the winding core according to the difference in surface roughness between the separator 130 and the winding core.

2 is a flowchart of a method for manufacturing a jelly-roll type electrode assembly according to an embodiment of the present invention. 3 is a side view of a winding core used in a jelly-roll type electrode assembly manufacturing method according to an embodiment of the present invention. 4 is a cross-sectional view of a winding core used in a jelly-roll type electrode assembly manufacturing method according to an embodiment of the present invention.

Referring to FIG. 2, the manufacturing method (S1000) of the electrode assembly 100 according to this embodiment,

Preparing a separator (S1100), comparing the surface roughness values of the separator and the winding core (S1200), adjusting the surface roughness of the winding core based on the compared value (S1300), and using the winding core to separate the separator and the electrode It may include a step (S1400) of winding a sheet-like laminate comprising a.

Hereinafter, prior to a more detailed description of the manufacturing method of the jelly-roll type electrode assembly according to an embodiment of the present invention, a winding core that can be used in the present manufacturing method will be described.

Referring to FIGS. 3 and 4 , the core 200 may have a long rod shape. A cross section of the winding core 200 may have a circular shape as a whole. One end of the winding core 200 may be separated based on a central axis, and cross sections of the separated parts may each have a semicircular shape. The separated parts may be referred to as a first part 210a and a second part 210b, respectively. A sheet-like laminate may be inserted between the first part 210a and the second part 210b facing each other in the winding core 200, and the sheet-like laminate is formed on the outer surface of the winding core 200 ( 220) can be wound along. Through the rotation of the winding core 200, the sheet-like laminate can be wound in a jelly-roll shape. In the jelly-roll type electrode assembly 100, the winding core 200 may be positioned on the core 100a. When the winding process is completed, the core 200 positioned on the core 100a may be removed from the jelly-roll type electrode assembly 100 .

Meanwhile, during the process of removing the winding core 200, the winding core 200 may not be discharged due to frictional force between the winding core 200 and the separator 130 located in the innermost layer of the electrode assembly 100. In addition, the separator 130 is damaged due to the frictional force between the separator 130 and the winding core 200, or a defect in which the separator 130 is pulled out of the electrode assembly 100 may occur, resulting in a decrease in production efficiency and electrode Disconnection of (110, 120) and internal short-circuit may cause problems that deteriorate the safety of the secondary battery. Therefore, in order to minimize this phenomenon, a flat portion 230 extending in the longitudinal direction may be formed on a portion of the outer surface 220 of the winding core 200 . Since the flat portion 230 is formed, the contact surface between the winding core 200 and the separator 130 can be minimized, and through this, problems that may occur when removing the winding core can be minimized. The length t1 of the flat portion 230 may correspond to the length of the sheet-like laminate, specifically, the length of the core 100a.

A distance between the first part 210a and the second part 210b into which the sheet-like laminate is inserted may be greater than the thickness of the sheet-like laminate. If the distance between the first part 210a and the second part 210b is similar to the thickness of the sheet-like laminate, the winding core 200 and the sheet-like laminate can be well fixed, but in the process of removing the winding core 200 A part of the sheet-like laminate may be damaged. The separation space between the first part 210a and the second part 210b, that is, the size g1 of the slit is fixed between the winding core 200 and the sheet-like laminate, but the contact between the winding core 200 and the sheet-like laminate needs to be designed to a level that is minimized. The size (g1) of the conventional slit is designed to be around 0.8 mm, but in this embodiment to which the double-sided SRS separator is applied, the size (g1) of the slit may be preferably 0.8 mm or more. It may be preferable that the size g1 of the slit in this embodiment be designed at a level of 0.8 to 1.2 mm.

The separator 130 may be provided as a double-sided SRS separator (S1100). A coating layer may be formed by applying a coating material to both sides of the separator 130 . The coating material may include ceramic particles and a polymer binder. The ceramic particles may include first alumina and second alumina, and a ratio of the second alumina may be within 40%. "Provision of the separation membrane 130" described in the step (S1100) can be interpreted as including both manufacturing the separation membrane 130 or putting the manufactured separation membrane 130 into this manufacturing process.

The provided separator 130 may be alternately stacked with the positive electrode 110 and the negative electrode 120 to form a sheet-like laminate. The sheet-like stacked body may be manufactured into a jelly-roll type electrode assembly 100 by being wound by a winding core 200 .

Prior to the winding process of the jelly-roll electrode assembly 100, the frictional force between the separator 130 and the winding core 200 may need to be adjusted in order to prevent damage to the separator 130 and loss of tails. To this end, the manufacturing process of the present embodiment may include calculating a difference in surface roughness between the separator 130 and the winding core 200 . Here, the surface roughness of the winding core 200 may mean the surface roughness of the outer surface 220 .

The surface roughness of the separator 130 and the winding core 200 is compared, and a difference between the two values can be calculated (S1200). The comparison of the surface roughness and the calculation of the difference value may be performed by a controller or a server of a device performing the present manufacturing method. The surface roughness of the separator 130 and the winding core 200 may be measured or obtained from a supplier of the separator 130 or the winding core 200 . Here, the surface roughness may be measured by a non-contact type or a contact type roughness meter, and for example, it may be measured by a Mitutoyo SJ-410 roughness meter. When the surface roughness values of the separator 130 and the winding core 200 are measured or obtained, the control unit or server may compare the measured or acquired surface roughness values and calculate a difference value.

Based on the calculated difference value, the surface roughness of the winding core 200 may be adjusted (S1300). In general, in order to improve the surface roughness of the workpiece, that is, the frictional force, prevention of frictional resistance according to the contact area, prevention of grooves due to surface roughness, prevention of grooves due to differences in hardness, or prevention of adhesion through surface treatment may be achieved. .

In improving the surface roughness of the core 200 as in the present embodiment, a polishing process such as sand blasting or lapping to minimize frictional resistance and prevent grooves by polishing the surface may be appropriate. In addition, when additional surface treatment is required, a surface treatment method such as DLC (Diamond Like Carbon) or CrN (Chrome Nitrate), which prevents adhesion by coating the surface, may be applied. Here, since the surface roughness of the winding core 200 is to improve the frictional force of the separator 130, different processes may be applied based on the difference in surface roughness between the winding core 200 and the separator 130.

Table 1 below shows the degree of finishing in the sanding process and lapping process, and Table 2 shows the processing level according to the finishing symbol. Here, Rmax may mean the maximum height of surface roughness, Rz may mean average roughness of 10 points, and Ra may mean average roughness of the center line.

sign ▽ ▽ ▽ ▽ ▽ ▽ ▽ ▽ ▽ ▽ sanding SB O O O O O O wrapping LP O O O O

Surface processing division value trim symbol nickname Rmax Rz Ra ▽ ▽ ▽ ▽ precision finishing 0.8s 0.8z 0.2a ▽ ▽ ▽ top finish 6.3s 6.3z 1.6a ▽ ▽ bottom trim 25s 25z 6.3a ▽ rough finish 100s 25z ~ no special regulations

The sanding process may be a process of polishing the surface of a workpiece by spraying fine particles of various materials onto the surface of the workpiece using high-pressure air or a high-speed rotating impeller. Uniform irregularities may be formed on the surface of the workpiece by the sanding process, and foreign matter remaining on the surface after processing may be removed. Here, the size of the particles used in the sanding process may be 120 to 150 mesh. 150mesh may mean a level of 106um.

The lapping process may be a precision machining method of finishing a workpiece by abrasion and grinding action using a tool called a lap and a lap agent. In the lapping process, the protrusions on the surface of the workpiece are removed by applying appropriate pressure to the wrapper against the workpiece, thereby improving surface precision and increasing the degree of contact between the contact surfaces. When the surface treatment of the core 200 is performed by a lapping process, the surface roughness may be 0.15 s to 0.25 s (Rmax), preferably 0.2 s (Rmax). Since the surface roughness of the winding core 200 is improved through the lapping process, damage to the separator 130 that may occur when the winding core 200 is removed can be prevented.

Referring to Tables 1 and 2, it can be seen that the polishing level of the lapping process is higher than that of the sanding process. Accordingly, when a difference in surface roughness between the winding core 200 and the separator 130 is large based on a specific reference value, a lapping process may be applied to improve the surface roughness of the winding core 200 . When the difference in surface roughness is not large, a sanding process may be applied to improve the surface roughness of the winding core 200 .

A difference in surface roughness between the winding core 200 and the separator 130 may be compared based on a predetermined value. If the difference in surface roughness is less than a predetermined value, the surface roughness of the winding core 200 and the separator 130 is similar. can

Therefore, in the step of adjusting the surface roughness of the winding core 200 based on the calculated difference value (S1300), if the difference in surface roughness between the winding core 200 and the separator 130 is less than the first value, the first process is applied. and applying a second process if the value is greater than or equal to the first value. Here, the first value may be 0.05s to 0.15s (Rmax), preferably 0.1s (Rmax). Also, the first process may be a sanding process, and the second process may be a lapping process.

Meanwhile, the manufacturing method of this embodiment may proceed to the step of winding the sheet-like laminate (S1400) after the above-described step of adjusting the surface roughness (S1300), but the surface roughness of the winding core 200 and the separator 130 Steps (S1200) and (S1300) may be repeatedly performed until the difference is less than the first value. This may be done so that the frictional force between the winding core 200 and the separator 130 is formed at a desired level by making the difference in surface roughness between the winding core 200 and the separator 130 less than or equal to the first value. At this time, the desired surface roughness of the winding core 200 may be 0.15 s to 0.25 s (Rmax), preferably 0.2 s (Rmax).

Specifically, when the surface roughness difference between the winding core 200 and the separator 130 calculated through step S1200 is greater than the first value, a lapping process may be applied to the winding core 200 through step S1300. Thereafter, the manufacturing method according to the present embodiment proceeds to step (S1200) again, and the surface roughness of the winding core 200 to which the lapping process is applied may be measured. Through step (S1200), the surface roughness value of the winding core 200 after the wrapping process is completed is confirmed, and the difference between the surface roughness of the winding core 200 and the surface roughness of the separator 130 after the wrapping process is completed can be calculated again. . If the calculated difference value is greater than or equal to the first value, the lapping process may be applied to the core 200 through step S1300, and step S1200 may be repeated again. If the calculated difference value is less than the first value, a sanding process may be applied to the winding core 200 through step S1300. Thereafter, the manufacturing method according to the present embodiment may proceed to step (S1400).

After the surface roughness of the winding core 200 is adjusted, a sheet-like laminate including a separator and an electrode may be wound using the winding core 200 (S1400). As described above, one end of the core 200 may include a first part 210a and a second part 210b cut with respect to the central axis. When one end of the sheet-like laminate is inserted into the slit between the first part 210a and the second part 210b, and the winding core 200 rotates in one direction, the sheet-like laminate is formed along the outer surface 220 of the winding core 200. can be rolled up At this time, since the surface roughness of the separation membrane 130 is adjusted by the ratio of the first alumina and the second alumina, the slip phenomenon and the like can be minimized.

Here, the size g1 of the slit is fixed between the winding core 200 and the sheet-type laminate, but needs to be designed to minimize contact between the winding core 200 and the sheet-type laminate. At this time, it may be preferable to design the size g1 of the slit to be 0.8 mm to 1.2 mm.

Although not shown, the manufacturing method of this embodiment may further include removing the core 200 from the jelly-roll type electrode assembly 100 . The separator 130 contacting the winding core 200 inside the electrode assembly 100 may have a surface roughness value adjusted by the ratio of the first alumina and the second alumina. In the above manufacturing method, the surface roughness between the winding core 200 and the separator 130 may be adjusted to a predetermined value or less. Therefore, it is possible to minimize the separation membrane 130 being pulled out of the rolled jelly-roll type electrode assembly 100 or the separation membrane 130 being damaged in the process of discharging the winding core 200 .

The manufacturing method of the jelly-roll type electrode assembly according to the present embodiment described above may be performed by a manufacturing apparatus of a jelly-roll type electrode assembly.

Specifically, the manufacturing apparatus includes a transfer unit for transporting the sheet-like assembly, a winding unit for winding the sheet-like assembly, a measuring unit for measuring the surface roughness of the separator 130 or the winding core 200, and the surface of the separator 130 or the winding core 200. It may include a control unit that compares roughness values and calculates a difference value, and a work unit that adjusts the surface roughness of the winding core 200 based on the difference value.

Here, the winding unit may include the aforementioned winding core 200 . The measuring unit may include a non-contact or contact roughness meter for measuring surface roughness. The working part may include a sanding device used in a sanding process and a lapping device used in a lapping process. The control unit may compare the measured surface roughness values, calculate a difference value, and control the overall operation of the above-described manufacturing apparatus. For example, the control unit may control the measuring unit to measure the surface roughness of the separator 130 or the winding core 200 . For another example, based on the measured value, the control unit may control the operation of the sanding or lapping device to perform the sanding or lapping process.

Hereinafter, experimental results of the jelly-roll type electrode assembly according to an embodiment of the present invention will be described.

Item unit Single-sided SRS
Double sided SRS thickness μm 12.9 12.6 13 12.7 basis weight/total weight g/m ² 8.29 7.9 8.3 8.21 primary alumina wt% 100 100 84 76 Secondary Alumina - - 16 24 Roughness
(Ra) Top
(fabric) Nm 180 201 550 930 Back (SRS) 610 Coefficient of friction
(static/kinetic) Sanding μk (PE) 0.44/0.33 0.76/0.72 0.67/0.67 0.67/0.67 Lapping (SRS) 0.23/0.21 0.31/0.28 0.27/0.23 0.27/0.23 Winding Test Results slip phenomenon no issue no issues no issues no issues automatic ejection
**Core specifications (gap=0.12mm, R=0.6mm)
Application of lapping process or sanding process no issues no issues
(Sanding+
Based on coating RT5000) no issues no issues
Separator damage

Table 3 is a test result of whether problems occurring during the winding process are improved according to the ratio of the first alumina and the second alumina included in the alumina mixture. In Table 3, it is noted in advance that alumina having a diameter of 500 nm was used as the second alumina in the case of the single-sided SRS, and alumina having a diameter of 300 nm was used as the second alumina in the case of the double-sided SRS. In addition, in the case of examples in which the double-sided SRS separator is applied, the step of adjusting the surface roughness of the winding core according to the manufacturing method of the above-described embodiment was applied, and thus the difference in surface roughness between the winding core and the double-sided SRS separator may be less than or equal to the first value.

In the case of the single-sided SRS separator presented as a comparison group, since the coating layer is formed on only one side of the fabric, the slip phenomenon may be less likely to occur than the double-sided SRS separator when winding the sheet-like laminate. In addition, in the case of using a single-sided SRS separator, since the winding is performed with the core on the side where the coating layer is not formed when winding the sheet-type laminate, fewer problems such as loss of tail or damage to the separator occur than in the case of using a double-sided SRS separator. can However, in the case of using a single-sided SRS separator, since the coating layer of the separator must be disposed to face the electrode, there is a problem in that the time required for the manufacturing process and the steps of the manufacturing process increase.

Looking at the experimental results for the double-sided SRS separator, it was confirmed that the slip phenomenon and the winding core discharge themselves did not cause a big problem in each example, but the damage to the separator was greater in the examples containing a low percentage of the second alumina. It became. This can be interpreted that when the coating layer is formed using only the first alumina having relatively small particles, the difference in surface roughness between the winding core and the coating layer is large, and as a result, the coating layer is more damaged when the winding core is discharged. In addition, in the examples of Table 3, the reason why the slip phenomenon did not appear even if the second alumina was included in a low ratio may be because the jelly-roll type electrode assembly 100 of the present examples is provided in a rather large size. For reference, in the experiment of Table 3, the length of the core 100a is about 10 to 12 cm, and the radius of the jelly-roll type electrode assembly 100 is 4 to 5 cm.

Specifically, when only the first alumina is included in the alumina mixture, the difference between the surface roughness of the separator 130 and the surface roughness of the winding core may be large. there is. In the past, a sanding process and a DLC coating process were applied to the winding core for this purpose, but there was a problem that the winding core was not discharged (automatic discharge issue), so it was not suitable for use in this embodiment.

Therefore, in this example, in order to improve the surface roughness of the winding core, a sanding process was applied to the winding core and a coating process (RT-5000) was applied. As a result, although the automatic discharge issue was improved compared to the case of using sanding and DLC coating, it was confirmed that the separator 130 was damaged during core discharge.

When the alumina mixture contained 16wt% of the second alumina, the automatic discharge issue was solved by applying some processes for adjusting the surface roughness of the winding core, but damage to the separator 130 was confirmed as in the above example.

However, when the alumina mixture contained 24wt% of the second alumina, it was found that the damage to the separator 130 was somewhat improved. Although not specifically described in the table, similar results were obtained even when the second alumina contained 40wt%. appear.

Referring to the above examples, it may be appropriate for the aluminum mixture used in the coating layer of the separator 130 to contain 24wt% or more of the second alumina. However, in the alumina mixture including the first alumina and the second alumina, the ratio of the first alumina and the second alumina may be appropriately adjusted depending on desired surface roughness and physical/electrochemical properties.

As the ratio of the second alumina increases, the surface roughness improves, so that the slip phenomenon, tail loss phenomenon or separator damage phenomenon that occurs during winding core discharge can be improved, but as the ratio of the first alumina having a small particle diameter increases, the air permeability and fixation of the coating layer As it is known that the force can be improved, it may be preferable that the ratio of the second aluminum is included within an appropriate value. For example, it may be appropriate that the second alumina is contained within 40 wt% of the alumina mixture. It may be appropriate that the second alumina is included within 24wt% to 40wt% of the alumina mixture.

In addition, as described above, an appropriate value of surface roughness may vary depending on the difference in roughness from the winding core, the width of the separator 130, or the size of the jelly-roll type electrode assembly 100. When the size of the jelly-roll electrode assembly 100 increases, the contact area between the winding core and the separator 130 increases, and the contact area between the rolled separator 130 and the electrodes 110 and 120 also increases, so tail loss phenomenon Alternatively, damage to the separation membrane 130 may occur more frequently.

When the size of the jelly-roll type electrode assembly 100 or the length of the core 100a is formed to be large, the surface roughness value of the separator 130 is designed to be somewhat large, and the jelly-roll type electrode assembly 100 or the core 100a When the length of ) is formed small, it may be desirable to design the surface roughness value of the separator 130 to be somewhat small. In the experiment of Table 3, the length of the core 100a is about 10 to 12 cm, and the radius of the jelly-roll type electrode assembly 100 is 4 to 5 cm. Therefore, when the size of the jelly-roll type electrode assembly 100 is designed to be smaller than this, the preferred ratio of the second alumina may be 24wt% or less. Specifically, when the second alumina is included in the alumina mixture at a level of 16wt% or 24wt%, the slip phenomenon does not appear during winding, and the tail loss phenomenon or damage to the separator 130 may not occur during winding core discharge. Therefore, it may be preferable that the second alumina is included in the alumina mixture in an amount of 16wt% or more. It may be appropriate that the second alumina is included within 16wt% to 24wt% of the alumina mixture. It may be appropriate that the second alumina is included within 16wt% to 40wt% of the alumina mixture.

In addition, the surface roughness (Ra) of the double-sided SRS separator may be 500 nm to 1 μm, preferably 550 nm to 930 nm.

To measure the surface roughness (Ra, nm), for example, after preparing a sample with a size of 300mm x 300mm, place a surface roughness measuring instrument (Mitutoyo SJ-210 model), and then set the built-in tip to 0.5mm. /s, the surface roughness is measured, and the Ra (nm) value, which is a parameter of the surface roughness, can be expressed numerically.

Meanwhile, the above-described jelly-roll type electrode assembly 100 according to the present embodiment may be included in a battery cell. The jelly-roll type electrode assembly 100 may be manufactured as a battery cell by inserting the cylindrical or prismatic metal container, filling the electrolyte, and sealing the metal container. The battery cell including the jelly-roll type electrode assembly 100 may be a cylindrical battery or a prismatic battery, but the shape of the battery cell including the jelly-roll type electrode assembly 100 is not limited to the above example.

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 of those skilled in the art using the basic concept of the present invention defined in the following claims are also made according to the present invention. falls within the scope of the rights of

100: electrode assembly
100a: core
110: anode
120: cathode
130: separator
200: Kwon Shim
210a: first part
210b: second part
220: turn away
230: flat part

Claims (19)

In a jelly-roll type electrode assembly in which a sheet-type laminate including an electrode and a separator is wound,
The separator includes a double-sided coating layer,
The coating layer includes a mixture of first alumina and second alumina,
The surface roughness (Ra) of the separator is 500 nm to 1 μm, and the particle diameter of the first alumina is smaller than the particle diameter of the second alumina jelly-roll type electrode assembly. In paragraph 1,
Based on 100 parts by weight of the mixture, the second alumina is included in 16 to 40 parts by weight of a jelly-roll type electrode assembly. In paragraph 2,
Based on 100 parts by weight of the mixture, the first alumina is included in 60 to 84 parts by weight of a jelly-roll type electrode assembly. In paragraph 1,
The particle diameter of the first alumina is 20 to 50 nm jelly-roll type electrode assembly. In paragraph 1,
The second alumina has a particle diameter of 300 to 500 nm jelly-roll type electrode assembly. In paragraph 1,
The electrode assembly is a jelly roll-type electrode assembly that is a double-sided SRS laminated in the order of a separator, an anode, a separator, and a cathode. In paragraph 1,
The length of the core of the jelly-roll-type electrode assembly is about 10 cm to 12 cm, and the radius is about 4 cm to 5 cm. Providing a separator comprising a double-sided coating layer;
Calculating a difference value between the surface roughness of the separator and the winding core;
When the difference between the separator and the surface roughness of the winding core is less than a first value, the surface roughness of the winding core is adjusted using a first process,
If the difference between the separator and the surface roughness value of the winding core is equal to or greater than the first value, adjusting the surface roughness of the winding core using a second process, and
Winding a sheet-like laminate including an electrode and the separator using the winding core whose surface roughness is controlled,
The coating layer includes a mixture of first alumina and second alumina,
The surface roughness (Ra) of the separator is 500 nm to 1 μm, and the particle diameter of the first alumina is smaller than the particle diameter of the second alumina. Method of manufacturing a jelly-roll type electrode assembly. In paragraph 8,
Based on 100 parts by weight of the mixture, the second alumina is included in 16 to 40 parts by weight of a jelly-roll type electrode assembly. In paragraph 9,
Based on 100 parts by weight of the mixture, the first alumina is included in 60 to 84 parts by weight of a jelly-roll type electrode assembly. In paragraph 8,
The first value (Rmax) is between 0.05s and 0.15s jelly-roll type electrode assembly manufacturing method. In paragraph 8,
The first process is a sanding process, a method of manufacturing a jelly-roll type electrode assembly. In paragraph 8,
The second process is a method of manufacturing a jelly-roll type electrode assembly that is a lapping process. In paragraph 8,
The sheet-like laminate is wound by a rod-shaped core,
The winding core includes a first part and a second part separated about a rotation axis,
One end of the sheet-like laminate is fixed by being inserted into the slit between the first part and the second part,
The size of the slit is greater than 0.8 mm jelly-roll method of manufacturing an electrode assembly. In paragraph 8,
The sheet-like laminate is wound by a rod-shaped core,
The surface roughness of the winding core is less than or equal to the second value,
The second value (Rmax) is 0.15 s to 0.25 s jelly-roll manufacturing method of the electrode assembly. In paragraph 8,
When the second process is used in the step of adjusting the surface roughness of the winding core, the step of calculating the difference between the surface roughness of the separator and the winding core is performed again. Manufacturing method of a jelly-roll type electrode assembly. In clause 16,
If the difference in surface roughness calculated in the step of calculating the difference between the surface roughness of the separator and the winding core, which was performed again, is equal to or greater than the first value, the step of adjusting the surface roughness of the winding core is performed using a second process. Method for manufacturing a jelly-roll type electrode assembly. In clause 16,
If the difference in surface roughness calculated in the step of calculating the difference between the surface roughness of the separator and the winding core is less than the first value, the step of adjusting the surface roughness of the winding core is performed using a first process. become,
A method of manufacturing a jelly-roll type electrode assembly, wherein the step of winding a sheet-like laminate including an electrode and the separator is performed using the winding core having the controlled surface roughness. A battery cell comprising the jelly-roll type electrode assembly according to claim 1.

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