Jelly roll type electrode assembly and method for manufacturing the same

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 laminate including an electrode and a separator is wound up, the separator includes a double-sided coating layer, the coating layer includes 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 per 100 parts by weight of the mixture, and the particle diameter of the first alumina is smaller than that of the second alumina.

Description

Technical Field

[0001] Cross - reference to related application(s) This application claims the benefit of priority based on Korean Patent Application No. 10 - 2021 - 0094709 filed on July 20, 2021 and Korean Patent Application No. 10 - 2022 - 0088832 filed on July 19, 2022, and all the contents disclosed in the documents of the Korean patent applications are included as part of this specification.

[0002] The present invention relates to a jelly - roll type electrode assembly and a method for manufacturing the same, and more specifically, to a jelly - roll type electrode assembly with improved safety and high process yield and a method for manufacturing the same.

Background Art

[0003] In modern society, the use of portable devices such as mobile phones, notebook computers, camcorders, and digital cameras has become common, and the development of technologies in fields related to such mobile devices has become active. In addition, rechargeable secondary batteries are used as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), plug - in hybrid electric vehicles (P - HEVs), etc. as a solution to problems such as air pollution caused by conventional gasoline vehicles that use fossil fuels. Therefore, the need for the development of secondary batteries is increasing.

[0004] Currently commercialized secondary batteries include nickel - cadmium batteries, nickel - metal hydride batteries, nickel - zinc batteries, lithium secondary batteries, etc. Among them, lithium secondary batteries have the advantages of being freely chargeable and dischargeable, having a low self - discharge rate, and a high energy density, and are in the spotlight.

[0005] Secondary batteries are classified into cylindrical batteries and prismatic batteries in which the electrode assembly is incorporated into a cylindrical or prismatic metal can according to the shape of the battery case, and pouch - type batteries in which the electrode assembly is incorporated into a pouch - type case of an aluminum laminate sheet.

[0006] Secondary batteries may be classified according to the structure of the electrode assembly in which a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes are laminated. Typically, there are a jelly roll type (winding type) electrode assembly in which a long sheet-type positive electrode and negative electrode are wound with a separator interposed therebetween, and a stack type (laminated type) electrode assembly in which a plurality of positive electrodes and negative electrodes cut out in units of a predetermined size are sequentially laminated with a separator interposed therebetween. 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 hybrid form of the jelly roll type and the stack type, has also been developed. Among them, the jelly roll type electrode assembly is the easiest to manufacture and has the merit of high energy density per unit weight.

[0007] A separator is a film material that has the function of separating two electrodes (positive electrode / negative electrode) in a secondary battery, blocking an electrical short circuit due to physical contact, and providing a path through which ions can move between the two electrodes through an electrolytic solution supported in fine pores, so as to have ion conductivity. In the case of secondary batteries for electric vehicles, different from existing small electronic devices, heat resistance characteristics are required to ensure the safety of the battery even in an environment exposed to heat of about 150°C. As a result, recently, polypropylene (PP) with excellent thermal properties has been used as a material for the separator, and a ceramic coating SRS (safety reinforced separator) separator with improved heat resistance by coating ceramic particles and a polymer binder on one or both sides of the separator has been applied to secondary batteries.

[0008] On the one hand, when applying a double-sided SRS separation membrane to a jelly roll type electrode assembly, there was a problem that the process yield was slightly reduced due to the surface roughness value of the SRS separation membrane and the core, or the frictional force between the SRS separation membrane and the core associated therewith. Specifically, when applying the double-sided SRS separation membrane, a slip phenomenon may occur due to the frictional force of the coating layer formed on the separation membrane or the difference in frictional force between the core and the separation membrane, and a tail-out phenomenon may occur when removing the core, making it difficult to ensure the processability of the jelly roll type electrode assembly.

[0009] Therefore, in order to solve such problems of the conventional technology, there is a need for a jelly roll type electrode assembly and a method for manufacturing the same that take into account the surface roughness values of the SRS separation membrane and the core.

Summary of the Invention

Problems to be Solved by the Invention

[0010] The problem to be solved by the present invention is to provide a jelly roll type electrode assembly with improved safety and high process yield and a method for manufacturing the same.

[0011] However, the problems to be solved by the embodiments of the present invention are not limited to the above-mentioned problems, and can be variously extended within the scope of the technical idea included in the present invention.

Means for Solving the Problems

[0012] A jelly roll type electrode assembly in which a sheet-like laminate including an electrode and a separation membrane according to an embodiment of the present invention is wound, wherein the separation membrane includes a double-sided coating layer, the double-sided coating layer includes a mixture of first alumina and second alumina, the surface roughness Ra of the separation membrane is from 500 nm to 1 μm, and the particle diameter of the first alumina may be smaller than the particle diameter of the second alumina.

[0013] The second alumina may be included in an amount of 16 to 40 parts by weight with respect to 100 parts by weight of the mixture.

[0014] The first alumina may be included in an amount of 60 to 84 parts by weight with respect to 100 parts by weight of the mixture.

[0015] The particle diameter of the first alumina may be 20 to 50 nm.

[0016] The particle diameter of the second alumina may be 300 to 500 nm.

[0017] The electrode assembly (jelly roll type electrode assembly) may be a double-sided SRS laminate laminated in the order of a separator, a positive electrode, a separator, and a negative electrode.

[0018] 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.

[0019] The method for manufacturing a jelly roll type electrode assembly according to an embodiment of the present invention includes a step of providing a separator including a double-sided coating layer, a step of calculating a difference value between the surface roughnesses of the separator and the core, and when the difference between the surface roughness values of the separator and the core is less than a first value, adjusting the surface roughness of the core using a first process, and when the difference between the surface roughness values of the separator and the core is greater than or equal to the first value, adjusting the surface roughness of the core using a second process, and winding a sheet type laminate including an electrode and the separator using the core with the adjusted surface roughness, the double-sided coating layer includes a mixture of a first alumina and a 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.

[0020] The second alumina may be included in an amount of 16 to 40 parts by weight with respect to 100 parts by weight of the mixture.

[0021] The first alumina may be included in an amount of 60 to 84 parts by weight with respect to 100 parts by weight of the mixture.

[0022] The first value (Rmax) may be between 0.05 s and 0.15 s.

[0023] The first step may be a sanding step.

[0024] The second step may be a wrapping step.

[0025] The sheet-like laminate is wound by a rod-shaped core, the core includes a first part and a second part separated around a rotation axis, one end of the sheet-like laminate is fixed by being inserted into a slit between the first part and the second part, and the size of the slit may be larger than 0.8 mm.

[0026] The sheet-like laminate is wound by a rod-shaped core, the surface roughness of the core is equal to or less than a second value, and the second value (Rmax) may be from 0.15 s to 0.25 s.

[0027] When the second step is used in the step of adjusting the surface roughness of the core, the step of calculating the difference value between the surface roughness of the separator membrane and the core may be performed again.

[0028] In the step of calculating the difference value between the surface roughness of the separator membrane and the core that is performed again, if the calculated difference value of the surface roughness is equal to or greater than the first value, the step of adjusting the surface roughness of the core using the second step may be performed.

[0029] In the step of calculating the difference value between the surface roughness of the separator membrane and the core that is performed again, if the calculated difference value of the surface roughness is less than the first value, the step of adjusting the surface roughness of the core using the first step is performed, and the step of winding a sheet-like laminate including an electrode and the separator membrane may be performed using the core with the adjusted surface roughness.

[0030] A battery cell according to another embodiment of the present invention includes the jelly roll type electrode assembly described above.

Advantages of the Invention

[0031] According to the embodiment, the jelly roll type electrode assembly and the manufacturing method thereof of the present invention improve heat resistance and safety by including a double-sided SRS separation film, and can improve the process yield by adjusting the surface roughness of the SRS separation film and the core.

[0032] 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.

Brief Description of the Drawings

[0033]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0034] Hereinafter, with reference to the attached drawings, various embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. The present invention can be embodied in various different forms other than those described below, and the scope of the present invention is not limited to the embodiments described herein.

[0035] To clearly explain the present invention, parts not related to the explanation are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

[0036] Also, the sizes and thicknesses of the respective components shown in the drawings are arbitrarily enlarged or reduced for the sake of convenience of explanation, and it is obvious that the content of the present invention is not limited to what is shown. In the following drawings, the thicknesses of the respective layers are enlarged to clearly represent various layers and regions. And in the following drawings, for the sake of convenience of explanation, the thicknesses of some layers and regions are exaggeratedly shown.

[0037] Also, when a part such as a layer, film, region, or plate is said to be "on" or "above" another part, this must be interpreted to include not only the case where the corresponding part such as the layer, film, region, or plate is directly above the other part, but also the case where there are other parts in between. Conversely, when it is explained that the corresponding part such as the layer, film, region, or plate is "directly above" another part, it means that there are no other parts in between. Also, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" in the direction opposite to gravity. On the other hand, similar to explaining being "on" or "above" another part, explaining being "below" or "beneath" another part can also be understood with reference to the above content.

[0038] Also, throughout the specification, when a part "includes" a certain component, this means that, unless otherwise specified to the contrary, it does not exclude other components and may further include other components.

[0039] Also, throughout the specification, when it is "on a plane", this means when the corresponding part is viewed from above, and when it is "in a cross-section", this means when the cross-section cut out perpendicularly of the corresponding part is viewed from the side.

[0040] Hereinafter, a jelly roll type electrode assembly according to an embodiment of the present invention will be described.

[0041] FIG. 1 is a perspective view showing a jelly roll type electrode assembly according to an embodiment of the present invention.

[0042] 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 jelly roll type electrode assembly 100 is shown in which the separator 130, the positive electrode 110, the separator 130, and the negative electrode 120 are laminated in this order and wound so that the positive electrode 110 is located inside. However, this is not necessarily the case, and it is also possible to laminate the separator 130, the negative electrode 120, the separator 130, and the positive electrode 110 in this order so that the negative electrode 120 is located inside. Further, it is also possible to laminate them in the order of the positive electrode 110, the separator 130, the negative electrode 120, and the separator 130, or in the order of the negative electrode 120, the separator 130, the positive electrode 110, and the separator 130. In this way, the electrodes (positive electrode 110, negative electrode 120) and the separator 130 are alternately laminated to form a sheet-like laminate, and the sheet-like laminate may be wound by a long rod-shaped core.

[0043] The positive electrode 110 and the negative electrode 120 can be collectively referred to as electrodes (positive electrode 110, negative electrode 120). The electrodes (positive electrode 110, negative electrode 120) may be those in which a slurry containing an electrode active material is applied on a current collector. Here, the electrode slurry usually may contain, but is not limited to, an electrode active material, a conductive agent, a binder, and a solvent. Further, here, as the current collector, stainless steel, aluminum, copper, nickel, titanium, fired carbon, etc. may be used, and it may be provided in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a non-woven fabric body. 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 an alloy of any one of these.

[0044] The separator 130 can separate between the positive electrode 110 and the negative electrode 120 and provide a migration path for ions that migrate between the positive electrode 110 and the negative electrode 120. The separator 130 is a main component that affects the performance of the secondary battery. In order for the separator 130 to have physical properties suitable for the secondary battery, physical properties such as minimizing the thickness to reduce the electrical resistance and maximizing the porosity and the size of the pores must be satisfied. Also, electrochemical properties such as wettability with the electrolyte must be satisfied.

[0045] On the other hand, as the secondary battery is to be used in medium and large-sized devices, a problem has occurred in that when the temperature inside the battery cell rises to the level of 150 °C or higher, the separator 130 melts and an internal short circuit of the battery cell occurs. Therefore, since the separator 130 used in the secondary battery must satisfy heat resistance in addition to physical and electrochemical properties, there have been attempts to change the material of the separator 130 to polyolefin, polyethylene, polypropylene, or a composite thereof. Recently, mainly a method of manufacturing a separator 130 in which one or both surfaces of a porous substrate such as polyolefin, polyethylene, polypropylene, etc. are coated with a ceramic material coating material has been used. Such a separator 130 can be referred to as an SRS or SRS separator, and the detailed content regarding the SRS separator can be described with reference to known literature.

[0046] A coating layer can be formed by applying a coating material to one or both surfaces of the separator 130, and the heat resistance and safety of the separator 130 can be improved by the coating layer. For example, a coating material containing alumina (Al3O2) and a binder may be coated on one or both surfaces of the raw separator of the separator 130. When the raw separator is coated with alumina having strong heat resistance, the separator 130 can prevent an internal short circuit of the battery cell by physically and continuously blocking the contact between the positive electrode and the negative electrode even in a high-temperature state inside the battery cell such as thermal runaway.

[0047] The separation membrane 130 may be provided on both sides of the SRS separation membrane. Coating layers may be formed by applying a coating material to both of the two base fabrics of the separation membrane 130 facing the electrodes (positive electrode 110, negative electrode 120). When coating layers are formed on both sides of the separation membrane 130, either one of the one side or the other side of the separation membrane 130 may be in contact with the electrodes (positive electrode 110, negative electrode 120), so the arrangement of the separation membrane 130 is flexible within the process. Also, thereby, simplification of the process and reduction of the process time can be achieved.

[0048] The coating layer of the separation membrane 130 may contain ceramic particles and a polymer binder. Examples of the ceramic particles include alumina, and the characteristics of the separation membrane 130 may vary depending on the diameter of the alumina. For example, the smaller the diameter of the alumina, the larger the surface area of the particles, and a relatively large number of particles can contact the base fabric of the separation membrane 130, so the adhesion of the particles is improved and deformation of the separation membrane 130 can be suppressed. Also, when the coating material is repeatedly applied on the base fabric of the separation membrane 130, if the diameter of the particles is small, the thickness of the coating layer may become thin, so compared with the case where the diameter of the particles is large, the air permeability of the coating layer increases, and the ionic conduction resistance of the separation membrane 130 may become low. In order to embody the above-described effects, fine particle alumina with a small diameter may be used as the material of the coating material, and these diameters may be from 20 to 50 nm.

[0049] The coating layer of the separation membrane 130 may be formed on both sides, and the surface roughness of the separation membrane 130 may be determined by the coating layer. When forming the coating layer of the separation membrane 130 using fine particle alumina, the surface roughness of the coating layer may be low, and this may cause the separation membrane 130 to slip during the winding process (slip phenomenon). Also, if the surface roughness of the coating layer is excessively large, the separation membrane 130 may be cut or damaged during the winding process. In addition, depending on the surface roughness of the separation membrane 130, the separation membrane 130 may be pulled out with respect to the winding core or the separation membrane 130 may be damaged during the process of removing the winding core. Therefore, the surface roughness of the separation membrane 130 applied to the jelly roll type electrode assembly 100 must be appropriately adjusted.

[0050] The surface roughness of the separation membrane 130 may be adjusted by adjusting the particle size of the alumina contained in the coating material. As an 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 the fine particle alumina and general alumina contained in the mixture, an appropriate level of the coating layer required for the separation membrane 130 can be formed by varying the ratio of the two particles. At this time, the appropriate level of surface roughness may vary depending on the roughness difference with the winding core, the width of the separation membrane 130, or the size of the jelly roll type electrode assembly, so the appropriate mixture ratio may vary depending on each condition being changed. As will be described later, it is preferable that the mixture contains general alumina at a ratio of 40% or less. It is preferable that the mixture contains general alumina at a ratio of 16% or more.

[0051] Here, general alumina is for the purpose of distinction from fine particle alumina, and may refer to alumina particles having a larger diameter than fine particle alumina. The diameter of the general alumina may be 300 to 500 nm. Also, for convenience, fine particle alumina may be referred to as first alumina and general alumina may be referred to as second alumina.

[0052] Hereinafter, a method for manufacturing a jelly roll type electrode assembly according to an embodiment of the present invention will be described.

[0053] In the sheet-like laminate, since the length value of the separator 130 is larger than the length values of the electrodes (positive electrode 110, negative electrode 120), in the winding process, the winding core can contact one end of the separator 130 that extends longer from one end of the electrodes (positive electrode 110, negative electrode 120). Therefore, when the surface roughness difference between the separator 130 and the winding core is large, a problem may occur in that a part of the separator 130 is pulled out or the separator 130 is damaged when the winding core is discharged, and this may result in a low yield of the electrode assembly 100.

[0054] Thus, since the yield of the jelly roll type electrode assembly 100 may be reduced due to the surface roughness difference between the separator 130 and the winding core, it is necessary to adjust the surface roughness of the winding core in addition to changing the surface roughness of the separator 130. Therefore, the manufacturing method according to the present embodiment may include a process of adjusting the surface roughness of the winding core due to the surface roughness difference between the separator 130 and the winding core.

[0055] FIG. 2 is a flowchart of a method for manufacturing a jelly roll type electrode assembly according to an embodiment of the present invention. FIG. 3 is a side view of a winding core used in the method for manufacturing a jelly roll type electrode assembly according to an embodiment of the present invention. FIG. 4 is a cross-sectional view of a winding core used in the method for manufacturing a jelly roll type electrode assembly according to an embodiment of the present invention.

[0056] Referring to FIG. 2, the manufacturing method (S1000) of the electrode assembly 100 according to the present embodiment may include a step of preparing a separator (S1100), a step of comparing the surface roughness values of the separator and the winding core (S1200), a step of adjusting the surface roughness of the winding core based on the compared values (S1300), and a step of winding a sheet-like laminate including the separator and the electrodes using the winding core (S1400).

[0057] Before more specifically describing the method for manufacturing a jelly roll type electrode assembly according to an embodiment of the present invention, the core that can be used in this manufacturing method will be described.

[0058] Referring to FIGS. 3 and 4, the core 200 may have a long rod shape. The cross-section of the core 200 may have an overall circular shape. One end of the core 200 may be separated with respect to the central axis, and the cross-sections of the separated portions may each have a semi-circular shape. The separated portions can be respectively referred to as a first portion 210a and a second portion 210b. A sheet-type laminate may be inserted between the first portion 210a and the second portion 210b facing each other in the core 200, and the sheet-type laminate may be wound along the outer surface 220 of the core 200 by the rotation of the core 200 in one direction. Through the rotation of the core 200, the sheet-type laminate can be wound into a jelly roll type. In the jelly roll type electrode assembly 100, the core 200 may be located in the core 100a. When the winding process is completed, the core 200 located in the core 100a can be removed from the jelly roll type electrode assembly 100.

[0059] On the other hand, among the steps of removing the core 200, the core 200 may not be discharged due to the frictional force between the separator 130 located in the innermost layer of the electrode assembly 100 and the core 200. In addition, the separator 130 may be damaged due to the frictional force between the separator 130 and the core 200, or a defect may occur in which the separator 130 is pulled out of the electrode assembly 100, which may reduce the production efficiency, and problems such as disconnection of the electrodes (positive electrode 110, negative electrode 120) and internal short circuit may occur, which may also reduce the safety of the secondary battery. Therefore, in order to minimize such a phenomenon, a flat portion 230 extending in the longitudinal direction may be formed on a part of the outer surface 220 of the core 200. By forming the flat portion 230, the contact surface between the core 200 and the separator 130 can be minimized, and through this, the problems that may occur during the removal of the core can be minimized. The length t1 of the flat portion 230 can correspond to the length of the sheet-type laminate, specifically, the length of the core 100a.

[0060] The distance between the first part 210a and the second part 210b into which the sheet-shaped laminate is inserted may be larger than the thickness of the sheet-shaped laminate. When the distance between the first part 210a and the second part 210b is similar to the thickness of the sheet-shaped laminate, the space between the winding core 200 and the sheet-shaped laminate can be fixed properly, but in the process of removing the winding core 200, a part of the sheet-shaped 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, fixes the space between the winding core 200 and the sheet-shaped laminate, but the contact between the winding core 200 and the sheet-shaped laminate needs to be designed to be minimized. The size g1 of the conventional slit was designed to be around 0.8 mm, but in this embodiment where the double-sided SRS separation film is applied, the size g1 of the slit is preferably 0.8 mm or more. The size g1 of the slit in this embodiment is preferably designed at a level of 0.8 to 1.2 mm.

[0061] The separation film 130 may be provided on the double-sided SRS separation film (S1100). Coating layers may be formed by applying a coating material to both sides of the separation film 130. The coating material may include ceramic particles and a polymer binder. The ceramic particles may include first alumina and second alumina, and the ratio of the second alumina may be within 40%. The "provision of the separation film 130" described in step S1100 can be interpreted to include both the manufacturing of the separation film 130 and the introduction of the manufactured separation film 130 into this manufacturing process.

[0062] The provided separation film 130 can be alternately laminated with the positive electrode 110 and the negative electrode 120 to form a sheet-shaped laminate. The sheet-shaped laminate can be wound by the winding core 200 to manufacture the jelly roll type electrode assembly 100.

[0063] Prior to the winding process of the jelly roll type electrode assembly 100, in order to prevent damage to the separator 130 and tail-out phenomenon, etc., the frictional force between the separator 130 and the core 200 must be adjusted. For this purpose, the manufacturing process of this embodiment may include the step of calculating the difference value of the surface roughness between the separator 130 and the core 200. Here, the surface roughness of the core 200 may mean the surface roughness of the outer surface 220.

[0064] The surface roughness of the separator 130 and the core 200 may be compared, and the difference between the two values may be calculated (S1200). The comparison of the surface roughness and the calculation of the difference value may be performed by the control unit or the server of the apparatus for performing this manufacturing method. The surface roughness of the separator 130 and the core 200 may be measured respectively, or obtained from the provider of the separator 130 or the core 200. Here, the measurement of the surface roughness may be performed by a non-contact or contact type roughness meter. As an example, it may be measured by a Mitutoyo SJ-410 roughness meter or the like. When the surface roughness values of the separator 130 and the core 200 are measured or obtained, the control unit or the server can compare the measured or obtained surface roughness values and calculate the difference value.

[0065] Based on the calculated difference value, the surface roughness of the core 200 may be adjusted (S1300). Usually, in order to improve the surface roughness of the workpiece, that is, the frictional force, it is necessary to achieve prevention of frictional resistance according to the contact area, prevention of groove generation according to the surface roughness, prevention of groove generation due to the hardness difference, or prevention of adhesion through surface treatment.

[0066] In order to improve the surface roughness of the core 200 as in this embodiment, a polishing process that minimizes frictional resistance and prevents groove generation by polishing the surface, such as sandblasting or lapping, is appropriate. Additionally, when additional surface treatment is required, a surface treatment method such as DLC (Diamond Like Carbon) or CrN (Chrome Nitrate) that prevents adhesion by coating the surface may be applied. Here, since the surface roughness of the core 200 is for improving the frictional force of the separation membrane 130, different processes may be applied based on the difference value of the surface roughness between the core 200 and the separation membrane 130.

[0067] Table 1 below shows the finish levels of the sandblasting process and the lapping process, and Table 2 shows the processing levels according to the finish symbols. Here, Rmax means the maximum height of the surface roughness, Rz means the average roughness of 10 points, and Ra means the average roughness of the center line.

[0068]

Table 1

[0069]

Table 2

[0070] The sandblasting process is a process of finishing the surface of the 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 unevenness may be formed on the surface of the workpiece by the sandblasting process, and foreign matter on the surface remaining after processing may also be removed. Here, the size of the particles used in the sandblasting process may be at the 120 to 150 mesh level. 150 mesh means a level of 106 μm.

[0071] The lapping process is a precision machining method that finishes the workpiece by using a tool called a lap and a lapping agent through abrasion and grinding actions. In the lapping process, by applying the lap to the workpiece and applying appropriate pressure to make it operate, the protruding parts on the surface of the workpiece are removed, so the surface precision is improved and the contact degree of the contact surface is increased. When the surface treatment of the core 200 is performed by the lapping process, its surface roughness may be from 0.15s to 0.25sRmax, and preferably may also be at the 0.2sRmax level. Through the lapping process, by improving the surface roughness of the core 200, damage to the separation film 130 that may occur during the removal of the core 200 can be prevented.

[0072] Referring to Table 1 and Table 2, it can be seen that the polishing level of the lapping process is higher than that of the sanding process. Therefore, when the surface roughness difference between the core 200 and the separation film 130 is large based on a specific reference value, the lapping process can be applied to improve the surface roughness of the core 200. When the surface roughness difference is not large, the sanding process can be applied to improve the surface roughness of the core 200.

[0073] The difference in surface roughness between the core 200 and the separation film 130 can be compared based on a predetermined value. If the difference in surface roughness is less than the predetermined value, it can be interpreted that the surface roughness of the core 200 and the separation film 130 is similar, and if it is greater than or equal to the predetermined value, it can be interpreted that the difference in surface roughness between the core 200 and the separation film 130 is large.

[0074] Therefore, based on the calculated difference value, the step S1300 of adjusting the surface roughness of the core 200 may include the step of applying the first process when the surface roughness difference between the core 200 and the separation film 130 is less than the first value, and applying the second process when it is greater than or equal to the first value. Here, the first value may be from 0.05s to 0.15sRmax, and preferably may also be 0.1sRmax. Also, here, the first process may be the sanding process, and the second process may be the lapping process.

[0075] On the one hand, after the step S1300 of adjusting the surface roughness described above is performed, the manufacturing method of this embodiment may proceed to the step S1400 of winding up the sheet-like laminate, but steps S1200 and S1300 may be repeatedly performed until the surface roughness difference between the winding core 200 and the separation film 130 becomes less than the first value. This is to form the frictional force between the winding core 200 and the separation film 130 at a desired level by making the difference value of the surface roughness between the winding core 200 and the separation film 130 be equal to or less than the first value. At this time, the desired surface roughness of the winding core 200 may be from 0.15 s to 0.25 sRmax, and preferably may be at the level of 0.2 sRmax.

[0076] Specifically, when the surface roughness difference between the winding core 200 and the separation film 130 calculated through step S1200 is equal to or greater than the first value, a wrapping process may be applied to the winding core 200 through step S1300. Next, the manufacturing method according to this embodiment may proceed to step S1200 again, and the surface roughness of the winding core 200 to which the wrapping process has been applied may be measured. The surface roughness value of the winding core 200 for which the wrapping process has been completed through step S1200 is confirmed, and the difference value of the surface roughness between the winding core 200 for which the wrapping process has been completed and the separation film 130 may be calculated again. If the calculated difference value is equal to or greater than the first value, a wrapping process is applied to the winding 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. Next, the manufacturing method according to this embodiment may proceed to step S1400.

[0077] After the surface roughness of the core 200 is adjusted, a sheet-like laminate including a separation membrane and electrodes may be wound using the core 200 (S1400). As described above, one end of the core 200 may include a first portion 210a and a second portion 210b that are cut with respect to the central axis. One end of the sheet-like laminate is inserted into the slit between the first portion 210a and the second portion 210b, and when the core 200 rotates in one direction, the sheet-like laminate can be wound along the outer surface 220 of the core 200. At this time, since the surface roughness value of the separation membrane 130 is adjusted according to the ratio of the first alumina and the second alumina, slip phenomena and the like can be minimized.

[0078] Here, the size g1 of the slit fixes the space between the core 200 and the sheet-like laminate, but needs to be designed at a level that minimizes the contact between the core 200 and the sheet-like laminate. At this time, the size g1 of the slit is preferably designed at a level of 0.8 mm to 1.2 mm.

[0079] Although not shown, the manufacturing method of the present embodiment may further include a step of removing the core 200 from the jelly roll type electrode assembly 100. The separation membrane 130 that contacts the core 200 inside the electrode assembly 100 may be in a state where the surface roughness value is adjusted according to the ratio of the first alumina and the second alumina. The surface roughness between the core 200 and the separation membrane 130 can be adjusted to a predetermined value or less by the above-described manufacturing method. Therefore, in the process of discharging the core 200, it is possible to minimize the separation membrane 130 being pulled outside the jelly roll type electrode assembly 100 around which the separation membrane 130 is wound or the separation membrane 130 being damaged.

[0080] The manufacturing method of the jelly roll type electrode assembly according to the above-described present embodiment may be performed by a manufacturing apparatus for the jelly roll type electrode assembly.

[0081] Specifically, the manufacturing apparatus may include a transfer unit that transfers the sheet-shaped assembly, a winding unit that winds up the sheet-shaped assembly, a measurement unit that measures the surface roughness of the separation membrane 130 or the core 200, a control unit that compares the surface roughness values of the separation membrane 130 or the core 200 and calculates the difference value, and a machining unit that adjusts the surface roughness of the core 200 based on the difference value.

[0082] Here, the winding unit may include the aforementioned core 200. The measurement unit may include a non-contact or contact roughness meter that measures the surface roughness. The machining unit may include a sanding device used in the sanding process and a lapping device used in the lapping process. The control unit can not only compare the measured surface roughness values and calculate the difference value, but also control the overall operation of the aforementioned manufacturing apparatus. For example, the control unit can control the measurement unit to measure the surface roughness of the separation membrane 130 or the core 200. Another example is that based on the measured value, the control unit can control the operation of the sanding device or the lapping device so that the sanding process or the lapping process is performed.

[0083] Hereinafter, the experimental results of the jelly roll type electrode assembly according to an embodiment of the present invention will be described.

[0084]

Table 3

[0085] Table 3 above is the result of testing whether the problems occurring during the winding process are improved by the ratios of the first alumina and the second alumina contained in the alumina mixture. In Table 3, for the case of single-sided SRS, alumina with a diameter of 500 nm is used as the second alumina, and for the case of double-sided SRS, it is clarified in advance that alumina with a diameter of 300 nm is used as the second alumina. Also, in the case of the example applying the double-sided SRS separation membrane, the step of adjusting the surface roughness of the core is applied by the manufacturing method of the aforementioned embodiment, whereby the surface roughness difference between the core and the double-sided SRS separation membrane is below the first value.

[0086] In the case of the single-sided SRS separation membrane presented as the comparison group, since the coating layer is formed only on one side of the raw fabric, the slip phenomenon does not easily occur more frequently than in the case of the double-sided SRS separation membrane when the sheet-type laminate is wound. Also, when using the single-sided SRS separation membrane, since the winding core is placed on the side where the coating layer is not formed when winding the sheet-type laminate, problems such as the tail-out phenomenon or the separation membrane damage phenomenon occur less frequently than when using the double-sided SRS separation membrane. However, when using the single-sided SRS separation membrane, there is a problem of increasing the time required for the manufacturing process and the steps of the manufacturing process because the coating layer of the separation membrane must be arranged to face the electrode.

[0087] Looking at the experimental results for the double-sided SRS separation membrane, the slip phenomenon and the ejection of the winding core itself do not cause major problems in each example, but it was confirmed that more damage to the separation membrane occurred in the example where the second alumina was contained at a low ratio. This can be interpreted as follows: when the coating layer is formed using only the relatively small-particle first alumina, the surface roughness difference between the winding core and the coating layer is large, and thus the coating layer is more damaged when the winding core is ejected. Also, in the examples of Table 3, the fact that the slip phenomenon does not occur even when the second alumina is contained at a low ratio is because the jelly roll-type electrode assembly 100 of this example is provided in a somewhat larger size. For reference, the experiments in Table 3 were conducted when the length of the core 100a was about 10 to 12 cm and the radius of the jelly roll-type electrode assembly 100 was 4 to 5 cm.

[0088] Specifically, when only the first alumina is contained in the alumina mixture, the surface roughness of the separation membrane 130 formed thereby may have a large difference from the surface roughness of the winding core, so it is necessary to adjust the surface roughness of the winding core in order to improve this. Conventionally, a sanding process and a DLC coating process were sometimes applied to the winding core for this purpose, but there was a problem that the winding core was not ejected (automatic ejection issue), and it was not suitable for use in this embodiment.

[0089] Therefore, in this example, in order to improve the surface roughness of the core, a sanding process was applied to the core, and the 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 separation membrane 130 was damaged when the core was discharged.

[0090] Even when the alumina mixture contained 16 wt% of secondary alumina, the automatic discharge issue was solved by applying some processes to adjust the surface roughness of the core, but damage to the separation membrane 130 was confirmed as in the above example.

[0091] However, when the alumina mixture contained 24 wt% of secondary alumina, it was shown that such damage to the separation membrane 130 was somewhat improved, and although not specifically described in the table, similar results were shown when the secondary alumina content was 40 wt%.

[0092] Referring to the above example, it is appropriate that the alumina mixture used for the coating layer of the separation membrane 130 contains 24 wt% or more of secondary alumina. However, for an alumina mixture containing primary alumina and secondary alumina, the ratio of primary alumina to secondary alumina must be appropriately adjusted according to the desired surface roughness and physical / electrochemical properties, etc.

[0093] As the ratio of secondary alumina increases, the surface roughness improves, and the slip phenomenon, the tail-out phenomenon that occurs when the core is discharged, or the separation membrane damage phenomenon can be improved. However, it is known that as the ratio of primary alumina with a small particle diameter increases, the air permeability and adhesion of the coating layer can be improved. Therefore, it is preferable that the ratio of secondary alumina is within an appropriate value. For example, it is appropriate that the secondary alumina is contained within 40 wt% in the alumina mixture. It is appropriate that the secondary alumina is contained within 24 wt% to 40 wt% in the alumina mixture.

[0094] Also, as described above, the appropriate surface roughness value may vary depending on the roughness difference from the core, the width of the separation membrane 130, or the size of the jelly roll type electrode assembly 100. When the size of the jelly roll type electrode assembly 100 increases, the contact area between the core and the separation membrane 130 increases, and the contact area between the wound separation membrane 130 and the electrodes (positive electrode 110, negative electrode 120) also increases. Therefore, the tail-out phenomenon or damage to the separation membrane 130 may occur more frequently.

[0095] 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 separation membrane 130 is preferably designed to be slightly larger. When the length of the jelly roll type electrode assembly 100 or the core 100a is formed to be small, the surface roughness value of the separation membrane 130 is preferably designed to be slightly smaller. The experiment in Table 3 is the case where 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 is 24 wt% or less. Specifically, when the second alumina is contained in the alumina mixture at a level of 16 wt% or 24 wt%, the slip phenomenon may not occur during winding, and the tail-out phenomenon or damage to the separation membrane 130 may not occur when the core is discharged. Therefore, the second alumina is preferably contained in the alumina mixture at 16 wt% or more. It is appropriate that the second alumina is contained in the alumina mixture within 16 wt% to 24 wt%. It is appropriate that the second alumina is contained in the alumina mixture within 16 wt% to 40 wt%.

[0096] Also, the surface roughness Ra of the double-sided SRS separation membrane may be from 500 nm to 1 μm, and preferably may be from 550 nm to 930 nm.

[0097] The measurement of the surface roughness Ra, in nm, can be carried out as follows. For example, after manufacturing a sample of the produced test piece to a size of 300 mm × 300 mm, place a surface roughness measuring instrument (Mitutoyo SJ - 210 model). Then, set the speed of the built - in chip to 0.5 mm / s to measure the surface roughness, and the Ra (nm) value, which is a parameter of the surface roughness, can be digitized and shown.

[0098] On the other hand, the jelly - roll - type electrode assembly 100 according to the present embodiment described above may be included in a battery cell. After the jelly - roll - type electrode assembly 100 is inserted into a cylindrical or rectangular metal container, it may be filled with an electrolyte and the metal container may be sealed to manufacture a battery cell. The battery cell including the jelly - roll - type electrode assembly 100 may be a cylindrical battery or a rectangular battery, but the shape of the battery cell including the jelly - roll - type electrode assembly 100 is not limited to the examples described above.

[0099] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art using the basic concepts of the present invention defined in the following claims also belong to the scope of the present invention.

Explanation of Reference Numerals

[0100] 100: Electrode assembly 100a: Core 110: Positive electrode 120: Negative electrode 130: Separator 200: Winding core 210a: First part 210b: Second part 220: Outer surface 230: Flat part

Claims

1. In a jelly roll type electrode assembly in which a sheet-like laminate including an electrode and a separator is wound, the separator includes double-sided coating layers, the double-sided coating layers include a mixture of first alumina and second alumina, the surface roughness Ra of the separator is from 500 nm to 1 μm, the particle diameter of the first alumina is smaller than the particle diameter of the second alumina, with respect to 100 parts by weight of the mixture, the second alumina is included in an amount of 16 to 40 parts by weight, with respect to 100 parts by weight of the mixture, the first alumina is included in an amount of 60 to 84 parts by weight, the particle diameter of the first alumina is from 20 to 50 nm, the particle diameter of the second alumina is from 300 to 500 nm, the jelly roll type electrode assembly.

2. The jelly roll type electrode assembly according to claim 1, which is a double-sided SRS laminate laminated in the order of a separator, a positive electrode, a separator, and a negative electrode.

3. The jelly roll type electrode assembly according to claim 1, wherein the length of the core of the jelly roll type electrode assembly is from 10 cm to 12 cm and the radius is from 4 cm to 5 cm.

4. providing a separator including double-sided coating layers, calculating a difference value between the surface roughnesses of the separator and the core, when the difference between the surface roughness values of the separator and the core is less than a first value, adjusting the surface roughness of the core using a first process, when the difference between the surface roughness values of the separator and the core is greater than or equal to the first value, adjusting the surface roughness of the core using a second process, including winding a sheet-like laminate including an electrode and the separator using the core with the adjusted surface roughness, the double-sided coating layers include a mixture of first alumina and second alumina, the surface roughness Ra of the separator is from 500 nm to 1 μm, and the particle diameter of the first alumina is smaller than the particle diameter of the second alumina, a method for manufacturing a jelly roll type electrode assembly.

5. The method for manufacturing a jelly roll type electrode assembly according to claim 4, wherein with respect to 100 parts by weight of the mixture, the second alumina is included in an amount of 16 to 40 parts by weight.

6. The method for manufacturing a jelly roll type electrode assembly according to claim 5, wherein with respect to 100 parts by weight of the mixture, the first alumina is included in an amount of 60 to 84 parts by weight.

7. The manufacturing method of the jelly roll type electrode assembly according to claim 4, wherein the first value (Rmax) is between 0.05 s and 0.15 s.

8. The manufacturing method of the jelly roll type electrode assembly according to claim 4, wherein the first step is a sanding step.

9. The manufacturing method of the jelly roll type electrode assembly according to claim 4, wherein the second step is a wrapping step.

10. The sheet-like laminate is wound by the rod-shaped core, The core includes a first part and a second part separated around a rotation axis, One end of the sheet-like laminate is fixed by being inserted into a slit between the first part and the second part, The manufacturing method of the jelly roll type electrode assembly according to claim 4, wherein the size of the slit is larger than 0.8 mm.

11. The sheet-like laminate is wound by the rod-shaped core, The surface roughness of the core is equal to or less than a second value, The manufacturing method of the jelly roll type electrode assembly according to claim 4, wherein the second value (Rmax) is from 0.15 s to 0.25 s.

12. In the step of adjusting the surface roughness of the core, when the second step is used, the step of calculating the difference value of the surface roughness between the separator and the core is performed again. The manufacturing method of the jelly roll type electrode assembly according to claim 4.

13. In the step of calculating the difference value of the surface roughness between the separator and the core that is performed again, when the calculated difference value of the surface roughness is equal to or greater than the first value, the step of adjusting the surface roughness of the core using the second step is performed. The manufacturing method of the jelly roll type electrode assembly according to claim 12.

14. In the step of calculating the difference value of the surface roughness between the separator and the core that is performed again, when the calculated difference value of the surface roughness is less than the first value, the step of adjusting the surface roughness of the core using the first step is performed, The step of winding a sheet-like laminate including an electrode and the separator is performed using the core with the adjusted surface roughness. The manufacturing method of the jelly roll type electrode assembly according to claim 12.

15. A battery cell including the jelly roll type electrode assembly according to any one of claims 1 to 3.

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