CN117280507A

CN117280507A - Wound electrode assembly and method of manufacturing the same

Info

Publication number: CN117280507A
Application number: CN202280033495.0A
Authority: CN
Inventors: 金秀晶; 柳德铉
Original assignee: LG Energy Solution Ltd
Current assignee: LG Energy Solution Ltd
Priority date: 2021-07-20
Filing date: 2022-07-20
Publication date: 2023-12-22

Abstract

The roll-type electrode assembly according to an embodiment of the present invention is a roll-type electrode assembly in which a sheet-type laminate including an electrode and a separator is wound, wherein: the separator includes a double-sided coating; the coating comprises a mixture of a first alumina and a second alumina; the second alumina is included in an amount of 16 to 40 parts by weight based on 100 parts by weight of the mixture; and the particle diameter of the first alumina is smaller than the particle diameter of the second alumina.

Description

Wound electrode assembly and method of manufacturing the same

Technical Field

Cross Reference to Related Applications

The present application claims the benefits of korean patent application No.10-2021-0094709 filed 20 at 7 months of 2021 and korean patent application No. 10-2022-0088803 filed 19 at 7 months of 2022, the contents of which are incorporated herein by reference in their entireties.

The present disclosure relates to a wound electrode assembly and a method of manufacturing the same, and more particularly, to a wound electrode assembly having improved safety and high process yield, and a method of manufacturing the same.

Background

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

The secondary batteries commercialized at present include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium secondary batteries. Among them, lithium secondary batteries have been the focus of attention because they have advantages such as free charge and discharge, and have very low self-discharge rate and high energy density.

The secondary battery may be classified into a cylindrical battery having an electrode assembly mounted in a cylindrical metal can, a prismatic battery having an electrode assembly mounted in a prismatic metal can, and a pouch-shaped battery having an electrode assembly mounted in a pouch-shaped case made of a laminated aluminum plate, based on the shape of the battery case.

The secondary battery may be classified based on the structure of an electrode assembly having a structure in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween. Typically, there may be mentioned a winding (winding) type structure in which a long sheet type positive electrode and a long sheet type negative electrode are wound with a separator interposed between the positive electrode and the negative electrode, a stacking (lamination) type structure in which a plurality of positive electrodes and negative electrodes cut into a predetermined unit size are sequentially stacked with the separator interposed between the positive electrode and the negative electrode, and the like. In recent years, in order to solve the problems caused by the wound electrode assembly and the stacked electrode assembly, a stacked/folded electrode assembly, which is a combination of the wound electrode assembly and the stacked electrode assembly, has been developed. Among them, the rolled electrode assembly has advantages of being easiest to manufacture and having high energy density per unit weight.

The separator is a film material that separates two electrodes (positive/negative electrodes) in a secondary battery to interrupt an electrical short circuit caused by physical contact and has a function of ion conductivity by providing a path through which ions can move between the two electrodes through an electrolyte supported in micropores. In the case of secondary batteries for electric vehicles, they are required to have heat resistance that ensures the safety of the batteries even in an environment exposed to heat of about 150 ℃ unlike conventional small-sized electronic devices. Accordingly, in recent years, polypropylene (PP) having excellent thermal properties has been used as a material of a separator, and a ceramic-coated SRS separator (safety-enhancing separator) that improves thermal resistance by coating ceramic particles and a polymer binder on one surface or both surfaces of the separator has been applied to a secondary battery.

On the other hand, when the double-sided SRS separator is applied to the wound electrode assembly, there is a problem in that the process yield is slightly lowered by the surface roughness values of the SRS separator and the mandrel or the frictional force between the SRS separator and the mandrel. In particular, when the double-sided SRS separator is applied, a slip state or a tail-off state during removal of the mandrel may occur according to a difference in friction force of a coating layer formed on the separator or friction force between the core and the separator, which makes it difficult to ensure workability of the wound electrode assembly.

Therefore, in order to solve the problems of the prior art, it is necessary to develop a winding type electrode assembly and a method of manufacturing the same, in consideration of the surface roughness values of the SRS separator and the mandrel.

Disclosure of Invention

Technical problem

An object of the present disclosure is to provide a rolled electrode assembly having improved safety and high process yield, and a method of manufacturing the same.

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

Technical solution

According to an aspect of the present disclosure, there is provided a rolled electrode assembly in which a sheet-like laminate including an electrode and a separator is rolled, wherein the separator includes a double-sided coating layer, wherein the coating layer includes a mixture of a first alumina and a second alumina, and wherein the separator has a surface roughness (Ra) of 500nm to 1 μm, and a particle diameter of the first alumina is smaller than a particle diameter of the second alumina.

The second alumina may be included in an amount of 16 to 40 parts by weight based on 100 parts by weight of the mixture.

The first alumina may be included in an amount of 60 to 84 parts by weight based on 100 parts by weight of the mixture.

The first alumina may have a particle diameter of 20nm to 50 nm.

The second alumina may have a particle diameter of 300nm to 500 nm.

The electrode assembly may be a double-sided SRS laminate in which a separator, a positive electrode, a separator, and a negative electrode are stacked in this order.

The rolled electrode assembly may have a core length of about 10cm to 12cm and a radius of about 4cm to 5 cm.

According to another aspect of the present disclosure, there is provided a method of manufacturing a rolled electrode assembly, the method including the steps of: providing a separator including a double-sided coating, calculating a difference between a surface roughness of the separator and a surface roughness of the mandrel, adjusting the surface roughness of the mandrel using a first process if the difference between the surface roughness of the separator and the surface roughness of the mandrel is less than a first value, adjusting the surface roughness of the mandrel using a second process if the difference between the surface roughness of the separator and the surface roughness of the mandrel is equal to or greater than the first value, and winding a sheet laminate including an electrode and the separator using the mandrel whose surface roughness has been adjusted, wherein the coating includes a mixture of a first alumina and a second alumina, and wherein the separator has a surface roughness (Ra) of 500nm to 1 μm and a particle diameter of the first alumina is less than a particle diameter of the second alumina.

The amount of the first alumina may be 60 to 84 parts by weight based on 100 parts by weight of the mixture.

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

The first process may be a sand blasting process.

The second process may be a grinding process.

The sheet laminate is wound by a rod-shaped mandrel comprising a first portion and a second portion separated about an axis of rotation, one end of the sheet laminate being secured by insertion into a slit between the first portion and the second portion, and the slit being greater than 0.8mm in size.

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

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

When the difference in the surface roughness calculated in the step of calculating the difference between the surface roughness of the spacer and the surface roughness of the mandrel, which is performed again, is equal to or greater than the first value, the step of adjusting the surface roughness of the mandrel using the second process may be performed.

When the difference in the calculated surface roughness is less than or equal to the first value in the step of calculating the difference between the surface roughness of the separator and the surface roughness of the mandrel, which is performed again, the step of adjusting the surface roughness of the mandrel using the first process is performed, and the step of winding the sheet laminate including the electrode and the separator using the mandrel whose surface roughness has been adjusted may be performed.

According to still another aspect of the present disclosure, there is provided a battery cell including the above-described wound electrode assembly.

Advantageous effects

According to embodiments, the winding type electrode assembly and the method of manufacturing the same of the present disclosure may improve heat resistance and safety by including a double-sided SRS separator, and process yield by adjusting surface roughness of the SRS separator and the mandrel.

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

Drawings

Fig. 1 is a perspective view illustrating a rolled electrode assembly according to an embodiment of the present disclosure.

Fig. 2 is a flowchart of a method for manufacturing a rolled electrode assembly according to an embodiment of the present disclosure;

Fig. 3 is a side view of a mandrel used in a method of manufacturing a wound electrode assembly according to an embodiment of the present disclosure; and

fig. 4 is a cross-sectional view of a mandrel used in a method of manufacturing a wound electrode assembly according to an embodiment of the present disclosure.

Detailed Description

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

Portions irrelevant to the description will be omitted to clearly describe the present disclosure, and like reference numerals denote like elements throughout the specification.

Further, for convenience of description, the size and thickness of each element shown in the drawings are arbitrarily enlarged or reduced, and thus, it is apparent that the disclosure is not limited to those shown in the drawings. In the drawings, the thickness of layers, regions, etc. are exaggerated for clarity. In the drawings, the thickness of some layers and regions are exaggerated for convenience of description.

In addition, it will be understood that when an element such as a layer, film, region or sheet is referred to as being "on" or "over" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, it means that there are no other intervening elements present. Further, the word "upper" or "above" means being arranged on or below the reference portion, and does not necessarily mean being arranged on an upper end portion of the reference portion that is directed to the opposite direction of gravity. Meanwhile, similarly to the case where it is described as being located "on" or "above" another portion, the case where it is described as being located "under" or "below" another portion will also be understood with reference to the above.

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

Further, throughout the present specification, when referred to as a "plane", means a case where the target portion is viewed from the upper side, and when referred to as a "cross section", means a case where the target portion is viewed from the side of a vertically cut cross section.

Next, a wound electrode assembly according to an embodiment of the present disclosure will be described.

Referring to fig. 1, the wound electrode assembly 100 of the present 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 wound electrode assembly 100 in which a separator 130, a cathode 110, a separator 130, and an anode 120 are stacked in this order and wound such that the cathode 110 is located inside the wound electrode assembly 100 is shown, but this is not necessarily the case, and the separator 130, the anode 120, the separator 130, and the cathode 110 may also be stacked in this order such that the anode 120 is located inside. Further, the positive electrode 110, the separator 130, the negative electrode 120, and the separator 130 may be stacked in this order, or the negative electrode 120, the separator 130, the positive electrode 110, and the separator 130 may be stacked in this order. In this way, the electrodes 110 and 120 and the separator 130 are alternately stacked to form a sheet laminate, wherein the sheet laminate may be wound by a long rod-shaped mandrel.

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 formed by coating a slurry including an electrode active material on a current collector. Here, the electrode paste may generally include an electrode active material, a conductive material, a binder, and a solvent, but is not limited thereto. Further, the current collector herein may be stainless steel, aluminum, copper, nickel, titanium, calcined carbon, etc., and may be provided in various forms such as films, sheets, foils, nets, porous bodies, foam bodies, non-woven fabrics structures. Examples of the current collector for the positive electrode 110 may include aluminum or an alloy thereof, and examples of the current collector for the negative electrode 120 may include copper, nickel, stainless steel, or an alloy of any of them.

The separator 130 may separate the positive electrode 110 and the negative electrode 120, and may provide a moving channel of ions moving between the positive electrode 110 and the negative electrode 120. As a main component determining the performance of the secondary battery, the separator 130 should satisfy physical properties such as minimizing thickness to reduce resistance and maximizing porosity and pore size in order for the separator 130 to have physical properties suitable for the secondary battery. In addition, the separator 130 should also satisfy electrochemical properties such as wettability with an electrolyte.

Meanwhile, when the secondary battery is used in middle-and large-sized devices, the temperature inside the battery cell rises to a level of 150 deg.c or more, which causes the separator 130 to melt and causes problems of internal short circuits in the battery cell. Therefore, the separator 130 used in the secondary battery must satisfy heat resistance in addition to physical properties and electrochemical properties, and thus, attempts have been made to change the material of the separator 130 into polyolefin, polyethylene, polypropylene, or a composite body thereof. Recently, in addition to simply changing materials, a method of manufacturing the separator 130 in which one surface or both surfaces of a porous substrate such as polyolefin, polyethylene, polypropylene, or the like are coated with a coating material made of a ceramic material has been mainly used. Such a divider 130 may be referred to as an SRS or SRS divider, and details of the SRS divider may be described with reference to known documents.

The coating layer may be formed by applying a coating material to one surface or both surfaces of the separator 130, and heat resistance and safety of the separator 130 may be improved by the coating layer. For example, contain alumina (Al ₃ O ₂ ) And an adhesive may be coated on one surface or both surfaces of the distal end portion of the separator 130. When alumina having strong heat resistance is coated on the distal end portion, the separator 130 physically interrupts continuous contact between the positive electrode and the negative electrode even under high temperature conditions inside the battery cell, such as heat runaway, thereby preventing internal short circuits of the battery cell.

The spacer 130 may be provided as a double sided SRS spacer. The coating material may be coated on both surfaces of the distal end portion of the separator 130 facing the electrodes 110 and 120, thereby forming a coating layer. When the coating is formed on both surfaces of the separator 130, either one surface or the other surface of the separator 130 is in contact with the electrodes 110 and 120, so that the separator 130 can be freely arranged in the process. In addition, simplification of the process and reduction of the process time can be achieved accordingly.

The coating of the separator 130 may include ceramic particles and a polymer binder. Examples of the ceramic particles include alumina, and characteristics of the separator 130 may vary according to the diameter of the alumina. For example, as the diameter of the alumina decreases, the surface area of the particles increases, and a relatively large number of particles may be in contact with the distal end portion of the separator 130, thereby improving the adhesiveness of the particles, and deformation of the separator 130 may be suppressed. Further, even when the coating material is repeatedly applied to the distal end portion of the separator 130, if the particle diameter is small, the thickness of the coating layer may be thinned. Therefore, compared to the case where the particle diameter is large, the air permeability of the coating layer can be increased, and the ion-conductive resistance of the separator 130 can be reduced. In order to achieve the above effect, fumed alumina having a small diameter can be used as the material of the coating material, and their diameter can be 20nm to 50nm.

The coating of the separator 130 may be formed on both surfaces, and the surface roughness of the separator 130 may be determined by the coating. When the coating layer of the separator 130 is formed using fumed alumina, the surface roughness of the coating layer may become low, and thus, a phenomenon (slip state) in which the separator 130 slips during the winding process may occur. In addition, if the surface roughness of the coating layer is too large, a phenomenon in which the separator 130 may be cut or damaged during the winding process may occur. Further, in the course of removing the spindle, depending on the surface roughness of the separator 130, a phenomenon in which the separator 130 is pulled out along the spindle or the separator 130 is damaged may occur. Therefore, the surface roughness of the separator 130 applied to the rolled electrode assembly 100 should be appropriately adjusted.

The surface roughness of the separator 130 may be adjusted by adjusting the particle size of alumina contained in the coating material. In one example, the coating material may include a mixture of fumed alumina and ordinary alumina. Since the surface roughness of the coating layer may be changed according to the ratio of fumed alumina and general alumina contained in the mixture, an appropriate level of coating layer required for the separator 130 may be formed by changing the ratio of the two particles. At this time, an appropriate level of surface roughness may vary according to a difference from the mandrel in roughness, a width of the separator 130, or a size of the wound electrode assembly. Thus, as each condition is changed, the proportion of the appropriate mixture may vary. As will be described later, the mixture may preferably contain ordinary alumina in a proportion of 40% or less. The mixture may preferably contain conventional alumina in a proportion of 16% or more.

Here, the general alumina is used to distinguish from fumed alumina, and may refer to alumina particles having a larger diameter than fumed alumina. The diameter of the conventional alumina may be 300nm to 500nm. Further, for convenience, fumed alumina can be referred to as first alumina and ordinary alumina can be referred to as second alumina.

Next, a method of manufacturing a rolled electrode assembly according to an embodiment of the present disclosure will be described.

Since the length value of the separator 130 in the sheet laminate is greater than the length values of the electrodes 110 and 120, the mandrel may be in contact with one end of the separator 130 extending from one distal end of the electrodes 110 and 120 during winding. Therefore, when the difference in surface roughness between the separator 130 and the mandrel is large, there may be a problem in that a portion of the separator 130 is pulled out or the separator 130 is damaged when the mandrel is discharged, so that the yield of the electrode assembly 100 can be reduced.

As described above, the yield of the wound electrode assembly 100 may be reduced according to the difference in surface roughness between the separator 130 and the mandrel, and it is necessary to adjust the surface roughness of the mandrel in addition to changing the surface roughness of the separator 130. Accordingly, the manufacturing method according to the present embodiment may include a step of adjusting the surface roughness of the mandrel according to the difference between the surface roughness of the separator 130 and the surface roughness of the mandrel.

Fig. 2 is a flowchart of a method for manufacturing a rolled electrode assembly according to an embodiment of the present disclosure. Fig. 3 is a side view of a mandrel used in a method of manufacturing a wound electrode assembly according to an embodiment of the present disclosure. Fig. 4 is a cross-sectional view of a mandrel used in a method of manufacturing a wound electrode assembly according to an embodiment of the present disclosure.

Referring to fig. 2, the manufacturing method S1000 of the electrode assembly 100 according to the present embodiment may include,

a step S1100 of preparing the separator, a step S1200 of comparing the surface roughness values of the separator and the mandrel, a step S1300 of adjusting the surface roughness of the mandrel based on the compared values, and a step S1400 of winding a sheet laminate including the separator and the electrode using the mandrel.

Next, before a method of manufacturing a rolled electrode assembly according to an embodiment of the present disclosure is specifically described, a mandrel that can be used in the present manufacturing method will be described.

Referring to fig. 3 and 4, the spindle 200 may have a long rod shape. The cross-section of the mandrel 200 may have a circular shape as a whole. One end of the spindle 200 may be separated based on the central axis, and the cross section of the separated portion may have a semicircular shape. The separated portions may be referred to as a first portion 210a and a second portion 210b, respectively. The sheet laminate may be interposed between the first portion 210a and the second portion 210b facing each other in the spindle 200, and may be wound along the outer surface 220 of the spindle 200 when the spindle 200 is rotated in one direction. By rotation of the spindle 200, the sheet laminate may be wound in a roll-type. In the winding type electrode assembly 100, the mandrel 200 may be positioned on the core body 100 a. When the winding process is completed, the mandrel 200 positioned in the core body 100a may be removed from the winding-type electrode assembly 100.

Meanwhile, during the process of removing the mandrel 200, the mandrel 200 may not be discharged due to friction between the separator 130 located at the innermost layer of the electrode assembly 100 and the mandrel 200. In addition, the separator 130 may be damaged by friction between the separator 130 and the mandrel 200, or the separator 130 may be pulled out of the electrode assembly 100, thereby reducing production efficiency, which may cause problems such as reduced safety of the secondary battery, including disconnection and internal short-circuiting of the electrodes 110 and 120. Accordingly, 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 spindle 200. By forming the flat portion 230, the contact surface between the spindle 200 and the separator 130 can be minimized, thereby minimizing problems that may occur during removal of the spindle. The length t1 of the flat portion 230 may correspond to the length of the sheet laminate, in particular, the length of the core 100 a.

The spacing between the first portion 210a and the second portion 210b into which the sheet laminate is inserted may be greater than the thickness of the sheet laminate. If the spacing between the first portion 210a and the second portion 210b is similar to the thickness of the sheet laminate, the mandrel 200 and the sheet laminate may be satisfactorily secured, but a portion of the sheet laminate may be damaged during the process of removing the mandrel 200. The separation space between the first portion 210a and the second portion 210b, i.e. the dimension g1 of the slit, is fixed between the spindle 200 and the sheet laminate, but needs to be designed to minimize contact between the spindle 200 and the sheet laminate. The conventional slit size g1 is designed to be about 0.8mm, but in the present embodiment in which the double-sided SRS separator is applied, the slit size g1 may be preferably 0.8mm or more. The slit dimension g1 of the present embodiment may be preferably designed in a horizontal direction of 0.8mm to 1.2 mm.

The spacer 130 may be provided as a double-sided SRS spacer S1100. A coating material may be applied to both surfaces of the separator 130 to form a coating layer. The coating material may include ceramic particles and a polymeric binder. The ceramic particles may include a first alumina and a second alumina, wherein the proportion of the second alumina may be 40% or less. The "providing the separator 130" described in step S1100 may be interpreted to include those steps of manufacturing the separator 130 and those steps of inputting the manufactured separator to the present 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 laminate may be wound by the mandrel 200 and manufactured into the wound electrode assembly 100.

Prior to the winding step of the winding-type electrode assembly 100, it may be necessary to adjust the frictional force between the separator 130 and the mandrel 200 to prevent damage to the separator 130 and occurrence of a tail-out state. For this, the manufacturing process of the present embodiment may include a step of calculating a difference between the surface roughness of the separator 130 and the surface roughness of the mandrel 200. Here, the surface roughness of the mandrel 200 may refer to the surface roughness of the outer surface 220.

By comparing the surface roughness of the separator 130 and the surface roughness of the mandrel 200, a difference S1200 between the two values can be calculated. The comparison of the surface roughness and the calculation of the difference value may be performed by a control unit or a server of the apparatus for performing the present manufacturing method. The surface roughness of the separator 130 and the surface roughness of the mandrel 200 may be measured separately or may be obtained from a supplier of the separator 130 or the mandrel 200. The surface roughness measurement can be carried out by a noncontact or contact roughness tester. As an example, it can be measured by a SJ-410 roughness tester available from Mitutoyo. When measuring or acquiring the surface roughness values of the separator 130 and the spindle 200, the control unit or the server may compare the measured or acquired surface roughness values and calculate a difference value.

Based on the calculated difference, the surface roughness S1300 of the mandrel 200 may be adjusted. In general, in order to improve the surface roughness of a workpiece, that is, friction force, it is necessary to realize prevention of friction resistance due to a contact area, prevention of grooves/dents due to surface roughness, prevention of grooves/dents due to hardness difference, prevention of adhesion due to surface treatment, and the like.

As in the present embodiment, in order to improve the surface roughness of the mandrel 200, the surface is polished by sand blasting, grinding, or the like, whereby the polishing process of minimizing frictional resistance and preventing grooves/dents can be appropriately performed. Furthermore, if additional surface treatment is required, a surface treatment method such as DLC (diamond like carbon) or CrN (chromium nitrate) may also be applied, which prevents adhesion by coating the surface. Here, since the surface roughness of the spindle 200 is used to improve the friction of the separator 130, a different process may be applied based on a difference between the surface roughness of the spindle 200 and the surface roughness of the separator 130.

Table 1 below shows the polishing degree of the blasting process and the grinding process, and table 2 below shows the processing level according to the polishing symbol. Here, rmax represents the maximum height of the surface roughness, rz represents the average roughness of 10 points, and Ra may represent the average roughness of the center line.

[ Table 1 ]

[ Table 2 ]

The blasting 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. By the blasting process, uniform unevenness can be formed on the surface of the workpiece, and foreign matter remaining on the surface after processing can be removed. Here, the size of the particles used in the blasting process may be on the order of 120 mesh to 150 mesh. 150 mesh may represent a 106 μm level.

The grinding process may be a precision machining method in which a workpiece is polished by abrasion and grinding using a tool called a grinding disk and an abrasive material. The grinding process removes protruding portions on the surface of the workpiece by placing a grinding disk on the workpiece and applying an appropriate pressure to the workpiece, so that the surface accuracy is improved and the degree of contact of the contact surface is increased. When the surface treatment of the spindle 200 is performed by the grinding process, the surface roughness may be 0.15s to 0.25s (Rmax), preferably at a level of 0.2s (Rmax). Since the surface roughness of the mandrel 200 is improved by the grinding process, the separator 130 can be prevented from being damaged during the removal of the mandrel 200.

Referring to tables 1 and 2, it can be seen that the polishing level of the grinding process is higher than that of the blasting process. Accordingly, when the difference in surface roughness between the spindle 200 and the separator 130 is large based on a specific reference value, a grinding process may be applied to improve the surface roughness of the spindle 200. When the difference in surface roughness is not large, a sand blasting process may be applied to improve the surface roughness of the mandrel 200.

The difference in surface roughness between the mandrel 200 and the separator 130 may be compared based on a predetermined value. When the difference in surface roughness is less than a predetermined value, the surface roughness of the spindle 200 is similar to that of the separator 130, and when the difference is equal to or greater than the predetermined value, it can be interpreted that the difference between the surface roughness of the spindle 200 and that of the separator 130 is large.

Accordingly, the step S1300 of adjusting the surface roughness of the mandrel 200 based on the calculated difference may include a step of applying a first process if the difference between the surface roughness of the mandrel 200 and the surface roughness of the separator 130 is less than a first value, and a step of applying a second process if the difference is equal to or greater than the first value. The first value may be 0.05s to 0.15s (Rmax), preferably 0.1s (Rmax). Further, the first process herein may be a blasting process and the second process may be a grinding process.

Meanwhile, the manufacturing method of the present embodiment may be performed by winding the sheet-like laminate after the above-described step S1300 of adjusting the surface roughness, and the manufacturing method of the present embodiment may repeatedly perform steps S1200 and S1300 until the difference in surface roughness between the mandrel 200 and the separator 130 is less than the first value. This can be ensured by setting the difference in surface roughness between the spindle 200 and the separator 130 to be equal to or smaller than the first value, the friction force between the spindle 200 and the separator 130 being formed at a desired level. At this time, the desired surface roughness of the spindle 200 may be 0.15s to 0.25s (Rmax), preferably at a level of 0.2s (Rmax).

Specifically, when the difference between the surface roughness of the spindle 200 calculated through step S1200 and the surface roughness of the separator 130 is equal to or greater than the first value, the grinding process may be applied to the spindle 200 through step S1300. Thereafter, the manufacturing method according to the present embodiment returns to step S1200, and the surface roughness of the mandrel 200 to which the grinding process is applied may be measured. The surface roughness value of the mandrel 200, which has completed the grinding process, is confirmed through step S1200, and the difference between the surface roughness of the mandrel 200, which has completed the grinding process, and the surface roughness of the separator 130 may be calculated again. When the calculated difference is equal to or greater than the first value, the grinding process is applied to the spindle 200 through step S1300, and step S1200 may be repeated again. When the calculated difference is smaller than the first value, a blasting process may be applied to the spindle 200 through step S1300. Subsequently, the manufacturing method according to the present embodiment may proceed to step S1400.

After the surface roughness of the mandrel 200 is adjusted, the sheet laminate S1400 including the separator and the electrode may be wound using the mandrel 200. As described above, one end of the mandrel 200 may include a first portion 210a and a second portion 210b cut along a central axis. When one end of the sheet laminate is inserted into the slit between the first portion 210a and the second portion 210b and the mandrel 200 is rotated in one direction, the sheet laminate may be wound along the outer surface 220 of the mandrel 200. At this time, since the separator 130 is in a state where the surface roughness value is adjusted by the ratio of the first alumina to the second alumina, the slip condition or the like can be minimized.

Here, the dimension g1 of the slit is fixed between the spindle 200 and the sheet laminate, but needs to be designed so as to minimize contact between the spindle 200 and the sheet laminate. At this time, the dimension g1 of the slit may be preferably designed at a level of 0.8mm to 1.2 mm.

Although not shown in the drawings, the manufacturing method of the present embodiment may further include a step of removing the mandrel 200 from the winding type electrode assembly 100. The separator 130, which is in contact with the mandrel 200 from the inside of the electrode assembly 100, may be in a state in which the surface roughness value is adjusted by the ratio of the first alumina to the second alumina. In the above-described manufacturing method, the surface roughness between the mandrel 200 and the separator 130 may be adjusted to a predetermined value or less. Accordingly, the separator 130 may be pulled out to the outside of the winding-type electrode assembly 100 or damage to the separator 130 may be minimized during the process of discharging the mandrel 200.

The above-described method for manufacturing a rolled electrode assembly according to the present embodiment may be performed by an apparatus for manufacturing a rolled electrode assembly. Specifically, the manufacturing apparatus may include a transfer unit that transfers the sheet assembly, a winding unit that winds the sheet assembly, a measuring unit that measures the surface roughness of the separator 130 or the spindle 200, a control unit that compares the surface roughness values of the separator 130 or the spindle 200 and calculates a difference value, and a processing unit that adjusts the surface roughness of the spindle 200 based on the difference value.

Here, the winding unit may include the above-described mandrel 200. The measuring unit may comprise a non-contact or contact roughness tester for measuring the surface roughness. The processing unit may comprise a blasting device for use in a blasting process and a grinding device for use in a grinding process. The control unit may not only compare the measured surface roughness values and calculate the difference values, but may also 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 spindle 200. In another example, based on the measured values, the control unit may control the operation of the blasting device or the grinding device so that the blasting process or the grinding process is performed.

Next, experimental results of the wound electrode assembly according to the embodiment of the present disclosure will be described.

[ Table 3 ]

Table 3 shows test results of whether or not the problem occurring during the winding process is improved according to the ratio of the first alumina and the second alumina contained in the alumina mixture. In table 3, it is previously clarified that in the case of the single-sided SRS, alumina having a diameter of 500nm is used as the second alumina, and in the case of the double-sided SRS, alumina having a diameter of 300nm is used as the second alumina. Further, in the case of applying the embodiment of the double-sided SRS spacer, the step of adjusting the surface roughness of the mandrel may be applied according to the manufacturing method of the above embodiment, and thus the difference in surface roughness between the mandrel and the double-sided SRS spacer may be less than or equal to the first value.

In the case of the single-sided SRS separator presented as the comparative group, the coating layer is formed on only one surface of the distal end portion, and therefore, when the sheet-like laminate is wound, a slip condition is less likely to occur than the double-sided SRS separator. Further, in the case of using the single-sided SRS separator, when winding the sheet-like laminate, the mandrel is placed and wound on the surface where no coating is formed, whereby problems such as a tail-off condition and damage to the separator may occur less than in the case of using the double-sided SRS separator. However, when the single-sided SRS separator is used, the coating of the separator must be disposed to face the electrode, which causes problems of an increase in the time required for the manufacturing process and the number of steps of the manufacturing process.

Experimental results observing the double sided SRS spacers demonstrate that in the corresponding embodiment, slip conditions and mandrel self-ejection do not cause significant problems, but in embodiments where the second alumina is included in a low proportion, damage to the spacers appears to be greater. This may be explained by the fact that when the coating is formed using only the first alumina having relatively small particles, the surface roughness difference between the spindle and the coating is large, which results in greater damage to the coating when the spindle is discharged. Further, the reason why the slippage condition does not occur even when the second alumina ratio included in the embodiment of table 3 is low is that the wound electrode assembly 100 of the present embodiment is provided in a slightly large size. For reference, the experiment of table 3 was a case where the length of the core 100a was about 10cm to 12cm, and the radius of the wound electrode assembly 100 was 4cm to 5 cm.

In particular, when only the first alumina is included in the alumina mixture, the surface roughness of the separator 130 thus formed may have a large difference from the surface roughness of the mandrel. Therefore, in order to improve this, it is necessary to adjust the surface roughness of the spindle. In the past, a sand blasting process and a DLC coating process were applied to the spindle for this purpose, but there was a problem that the spindle was not discharged (automatic discharge problem), so this was not suitable for use in the present example.

Therefore, in the present embodiment, in order to improve the surface roughness of the mandrel, a sand blasting process is applied to the mandrel, and a coating process (RT-5000) is applied. As a result, it was confirmed that the automatic discharge problem was improved as compared with the case of using the blasting and DLC coating, but the separator 130 was damaged when the mandrel was discharged.

When the alumina mixture contains 16wt.% of the second alumina, the automatic venting problem is solved by applying some process to control the surface roughness of the mandrel, but as exemplified above, damage to the separator 130 is confirmed.

However, if the alumina mixture contains 24wt.% of the second alumina, a slight improvement in damage to the separator 130 is shown, and although not specifically described in the table, similar results are obtained even when the amount of the second alumina contained is 40 wt.%.

With reference to the above embodiments, it may be appropriate that the aluminum mixture for the coating of the separator 130 contain 24wt% or more of the second aluminum oxide. However, in an alumina mixture comprising a first alumina and a second alumina, the ratio of the first alumina and the second alumina may need to be appropriately adjusted according to the desired surface roughness and physical/electrochemical properties.

As the proportion of the second alumina increases, the surface roughness is improved so that the slip condition and the tail drop condition or the separator damage phenomenon occurring when the mandrel is discharged can be improved, but it is known that as the proportion of the first alumina having a small particle diameter increases, the air permeability and the adhesiveness of the coating can be improved, whereby the proportion of the second aluminum can be preferably contained within a suitable value. For example, the second alumina may be suitably included in the alumina mixture in an amount of 40wt.% or less in the alumina mixture. The second alumina may suitably be included in the alumina mixture in an amount of 24wt.% to 40 wt.%.

Further, as described above, a suitable surface roughness value may vary according to a difference from the mandrel in terms of roughness, a width of the separator 130, or a size of the rolled electrode assembly 100. As the size of the wound electrode assembly 100 increases, the contact area between the mandrel and the separator 130 increases, and the contact area between the wound separator 130 and the electrodes 110 and 120 also increases, so that a tail-off condition or damage to the separator 130 may occur more frequently.

When the rolled electrode assembly 100 is formed to have a mandrel 100a of a larger size or length, the surface roughness value of the separator 130 is designed to be slightly larger, and when the rolled electrode assembly 100 or the core 100a is formed to be smaller, the surface roughness value of the separator 130 may preferably be designed to be slightly smaller. The experiment of table 3 was in the case where the length of the core 100a was about 10cm to 12cm, and the radius of the wound electrode assembly 100 was 4cm to 5 cm. Therefore, when the size of the rolled electrode assembly 100 is designed to be smaller than the above-described size, the preferred proportion of the second alumina may be 24wt.% or less. Specifically, when the second alumina is contained in the alumina mixture at a level of 16wt.% or at a level of 24wt.%, no tail-off condition or damage to the separator 130 occurs when the mandrel is discharged, while no slip condition occurs during winding. Thus, the second alumina may preferably be included in the alumina mixture in an amount of 16wt.% or more. The second alumina may suitably be included in the alumina mixture in an amount of from 16wt.% to 24 wt.%. The second alumina may suitably be included in the alumina mixture in an amount of from 16wt.% to 40 wt.%.

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

The surface roughness (Ra, nm) was measured as follows. For example, the prepared specimen was cut into dimensions of 300mm×300mm to prepare a sample, and a surface roughness tester (model SJ-210, mitutoyo) was mounted thereon, the built-in tip was set to measure surface roughness at a speed of 0.5mm/s, and Ra (nm) values as surface roughness parameters may be expressed numerically.

Meanwhile, the wound electrode assembly 100 according to the present embodiment described above may be included in a battery cell. The rolled electrode assembly 100 is inserted into a cylindrical or prismatic metal container, and then is filled with an electrolyte to seal the metal container, thereby manufacturing a battery cell. The battery cell including the rolled electrode assembly 100 may be a cylindrical battery or a prismatic battery, but the shape of the battery cell including the rolled electrode assembly 100 is not limited to the above example.

While the preferred embodiments of the present disclosure have been shown and described above, the scope of the present disclosure is not limited thereto, and many changes and modifications may be devised by those skilled in the art using the principles of the present invention as defined in the appended claims, which fall within the spirit and scope of the present disclosure.

Description of the reference numerals

100: electrode assembly

100a: core body

110: positive electrode

120: negative electrode

130: partition piece

200: mandrel

210a: first part

210b: second part

220: outer surface

230: a flat portion.

Claims

1. A wound-type electrode assembly in which a sheet-like laminate including an electrode and a separator is wound,

wherein the separator comprises a double-sided coating,

wherein the coating comprises a mixture of a first alumina and a second alumina, and

wherein the separator has a surface roughness (Ra) of 500nm to 1 μm, and the particle diameter of the first alumina is smaller than the particle diameter of the second alumina.

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

the second alumina is included in an amount of 16 to 40 parts by weight based on 100 parts by weight of the mixture.

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

the first alumina is included in an amount of 60 to 84 parts by weight based on 100 parts by weight of the mixture.

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

the first alumina has a particle diameter of 20nm to 50 nm.

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

the second alumina has a particle diameter of 300nm to 500 nm.

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

the electrode assembly is a double-sided SRS laminate in which a separator, a positive electrode, a separator, and a negative electrode are sequentially stacked.

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

the rolled electrode assembly has a core length of about 10cm to 12cm and a radius of about 4cm to 5 cm.

8. A method of manufacturing a rolled electrode assembly, the method comprising the steps of:

a separator comprising a double-sided coating is provided,

calculating a difference between the surface roughness of the separator and the surface roughness of the mandrel,

if the difference between the surface roughness of the separator and the surface roughness of the mandrel is less than a first value, the surface roughness of the mandrel is adjusted using a first process,

if the difference between the surface roughness of the separator and the surface roughness of the mandrel is equal to or greater than the first value, adjusting the surface roughness of the mandrel using a second process, and

Winding a sheet laminate including an electrode and the separator using the mandrel whose surface roughness has been adjusted,

9. The method of manufacturing a rolled electrode assembly according to claim 8, wherein:

10. The method of manufacturing a rolled electrode assembly according to claim 9, wherein:

11. The method of manufacturing a rolled electrode assembly according to claim 8, wherein:

the first value (Rmax) is between 0.05s and 0.15 s.

12. The method of manufacturing a rolled electrode assembly according to claim 8, wherein:

the first process is a sand blasting process.

13. The method of manufacturing a rolled electrode assembly according to claim 8, wherein:

The second process is a grinding process.

14. The method of manufacturing a rolled electrode assembly according to claim 8, wherein:

the sheet laminate is wound up by a rod-shaped mandrel,

the spindle includes first and second portions separated about an axis of rotation,

one end of the sheet-like laminate is fixed by being inserted into a slit between the first portion and the second portion, and

the size of the slit is larger than 0.8mm.

15. The method of manufacturing a rolled electrode assembly according to claim 8, wherein:

the sheet laminate is wound up by a rod-shaped mandrel,

the surface roughness of the mandrel is less than or equal to a second value, and

the second value (Rmax) is from 0.15s to 0.25s.

16. The method of manufacturing a rolled electrode assembly according to claim 8, wherein:

when the second process is used in the step of adjusting the surface roughness of the mandrel, the step of calculating a difference between the surface roughness of the separator and the surface roughness of the mandrel is performed again.

17. The method of manufacturing a rolled electrode assembly according to claim 16, wherein:

when the difference in the surface roughness calculated in the step of calculating the difference between the surface roughness of the separator and the surface roughness of the mandrel performed again is equal to or greater than a first value, the step of adjusting the surface roughness of the mandrel using a second process is performed.

18. The method of manufacturing a rolled electrode assembly according to claim 16, wherein:

when the difference in the surface roughness calculated in the step of calculating the difference between the surface roughness of the spacer and the surface roughness of the mandrel performed again is less than or equal to a first value, a step of adjusting the surface roughness of the mandrel using a first process is performed, and

a step of winding a sheet laminate including the electrode and the separator using the mandrel whose surface roughness has been adjusted is performed.

19. A battery cell comprising the rolled electrode assembly of claim 1.