Separator and electrochemical device including the same

Abstract

The present disclosure relates to a separator, an electrode assembly including the same, and an electrochemical device, and the separator according to one embodiment of the present disclosure comprises a porous substrate and a porous coating layer on each of both surfaces of the porous substrate, the porous coating layer comprising inorganic particles, in which a total thickness of the separator remains constant throughout the separator, wherein an aspect ratio of the separator is 1 or more, and wherein an interface between each of the porous coating layers and the porous substrate has a curved shape protruding toward the porous substrate based on a width direction of the separator.

Description

Technical Field

[0001] The present disclosure relates to a separator and an electrochemical device including the same. More particularly, the present disclosure relates to a separator for use in an electrode assembly manufactured by an advanced-Z-stacking (AZS) method.

[0002] This application claims priority to Korean Patent Application No. 2023-0050349 filed in Korea on April 17, 2023, the disclosure of which is incorporated herein by reference. Background Art

[0003] Secondary batteries can be classified according to the structure of the electrode assembly of the positive electrode / separator / negative electrode structure. Representative examples may include a jelly roll (winding) electrode assembly in which a long sheet positive electrode and a long sheet negative electrode are wound together with a separator inserted therebetween; a lamination and stacking (Lamination and Stacking, L&S) electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes obtained by cutting into a predetermined size are arranged together with a separator inserted therebetween to form a unit cell and a plurality of unit cells are stacked in a continuous order; and a zigzag stacking (Z-stacked) electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes obtained by cutting into a predetermined size are stacked layer by layer in a zigzag shape together with a long sheet separator inserted therebetween. However, these existing electrode assemblies have some problems.

[0004] Since the jelly roll (wound) electrode assembly is manufactured by tightly winding a long sheet positive electrode and a long sheet negative electrode to form a cylindrical or oval or elliptical cross-sectional structure, the stress caused by the expansion and contraction of the electrode during charge / discharge accumulates in the electrode assembly, and when the accumulated stress exceeds a predetermined limit, deformation occurs in the electrode assembly. The deformation in the electrode assembly causes the distance between the electrodes to be uneven, resulting in rapid performance degradation of the battery and internal short circuits that threaten the safety of the battery. In addition, when the long sheet positive electrode and the long sheet negative electrode are wound, it is difficult to quickly wind the positive and negative electrodes with a constant distance between the positive and negative electrodes, resulting in low productivity.

[0005] In contrast, L&S electrode assemblies and Z-stack electrode assemblies have higher stability and productivity than jelly-roll electrode assemblies and are gaining more attention. Nevertheless, research on these methods continues.

[0006] However, the L&S electrode assembly has the advantages of high sequential stacking speed of a plurality of positive electrode units and a plurality of negative electrode units and high space efficiency of the battery, but the misalignment of the separator may cause defects in the battery, so the sequential stacking process requires a lot of time and effort. Despite the high productivity, there is still a risk of instability. In addition, due to the use of long sheet separators, the Z-stacked electrode assembly provides a more stable structure than the L&S electrode assembly, but has low process efficiency due to process complexity.

[0007] Therefore, new electrode assembly manufacturing methods are continuously being researched and developed in an effort to obtain the advantages of L&S and the advantages of Z-stack and to compensate for their disadvantages.

[0008] For example, methods for manufacturing advanced Z-stack (AZS) electrode assemblies are being developed, and efforts are ongoing to improve productivity and stability of AZS electrode assemblies having large lengths.

[0009] Reference Figure 2b , an electrochemical device including an AZS electrode assembly that is long in the length direction (Y direction) is poorly wetted by the electrolyte at the center portion of the separator. Specifically, after electrolyte injection, a poorly wetted area or an unwetted area is observed at the center portion of the separator, resulting in low performance of a battery using the separator. Summary of the invention

[0010] Technical issues

[0011] The present disclosure is directed to providing a separator for use in an electrode assembly having improved productivity and stability, and an electrochemical device using the same.

[0012] In particular, the present disclosure is directed to providing a separator for use in an advanced Z-stack (AZS) electrode assembly. More particularly, the present disclosure is directed to providing a separator having improved electrolyte wettability throughout a lengthwise long AZS electrode assembly.

[0013] For example, the present disclosure is directed to providing a separator of a new structure that reduces or prevents a central portion from being non-wetted by an electrolyte.

[0014] Technical Solution

[0015] In order to solve the above problems, according to one aspect of the present disclosure, there is provided:

[0016] The separator of the following embodiment.

[0017] A separator according to a first embodiment includes:

[0018] a porous substrate, and

[0019] a porous coating on each of the two surfaces of the porous substrate, the porous coating comprising inorganic particles,

[0020] wherein the total thickness of the separator remains constant over the entire separator,

[0021] wherein the aspect ratio of the separator is 1 or greater, and

[0022] wherein an interface between each of the porous coating layers and the porous substrate has a curved shape convex toward the porous substrate based on a width direction of the separator.

[0023] According to a second embodiment, in the first embodiment,

[0024] The porous substrate may be thinnest at the center of the separator in the width direction.

[0025] According to a third embodiment, in the first embodiment or the second embodiment,

[0026] The porous base may be thickest at the outermost end of the separator in the width direction.

[0027] According to a fourth embodiment, in any one of the first to third embodiments,

[0028] The curved shape of the interface between the porous substrate and the porous coating layer may be symmetrical with respect to the center of the separator in the width direction.

[0029] According to a fifth embodiment, in any one of the first to fourth embodiments,

[0030] The curved shapes of the two interfaces may be symmetrical with respect to the center of the separator in the thickness direction.

[0031] According to a sixth embodiment, in any one of the first to fifth embodiments,

[0032] The thickness of the porous substrate may be 40% to 90% of 100% of the total thickness of the separator.

[0033] According to a seventh embodiment, in any one of the first to sixth embodiments,

[0034] The thickness of the porous substrate may be 45% to 65% of 100% of the total thickness of the separator.

[0035] According to an eighth embodiment, in any one of the first to seventh embodiments,

[0036] At 50% of the total width of the divider,

[0037] The thickness of the porous substrate may be 40% to 55% of the total thickness of the separator.

[0038] According to a ninth embodiment, in any one of the first to eighth embodiments,

[0039] At 0% or 100% of the total width of the divider,

[0040] The thickness of the porous substrate may be 50% to 70% of the total thickness of the separator.

[0041] According to a tenth embodiment, in any one of the first to ninth embodiments,

[0042] The length of the partition in the length direction may be 1.5 m to 5 m.

[0043] According to another aspect of the present disclosure, an electrode assembly according to the following embodiment is provided.

[0044] An electrode assembly according to an eleventh embodiment includes:

[0045] a cell positive electrode, a cell negative electrode, and a separator between the cell positive electrode and the cell negative electrode,

[0046] The separator is folded in a Z shape.

[0047] wherein the unit positive electrodes and the unit negative electrodes are arranged in an alternating manner at a plurality of regions where the separators are folded and overlapped, and

[0048] wherein the separator is as defined in any one of the first to tenth embodiments.

[0049] According to the twelfth embodiment, in the eleventh embodiment,

[0050] The cell positive electrode and the cell negative electrode may each include an electrode tab at an end.

[0051] According to still another aspect of the present disclosure, an electrochemical device according to the following embodiments is provided.

[0052] An electrochemical device according to a thirteenth embodiment includes:

[0053] The electrode assembly according to the eleventh embodiment or the twelfth embodiment and a case accommodating the electrode assembly.

[0054] According to the fourteenth embodiment, in the thirteenth embodiment,

[0055] The electrochemical device may be a lithium secondary battery.

[0056] According to the fifteenth embodiment, in the thirteenth embodiment or the fourteenth embodiment,

[0057] The housing may have a bag-type shape, a prism shape, a cylinder shape, or a coin-type shape.

[0058] Beneficial Effects

[0059] The separator according to one embodiment of the present disclosure has a shape in which the porous substrate has a smaller thickness at the center portion in one direction and the porous coating layer has a larger thickness. Thus, even if the size increases, the separator can reduce the area that is not wetted by the electrolyte at the center portion and can be fully wetted by the electrolyte over the entire area, thereby improving the wettability of the separator.

[0060] The separator according to one embodiment of the present disclosure can improve the wettability of the central portion, and thus improve the wettability of the entire separator, so that the length of the separator can be increased. Therefore, a high-performance electrochemical device can be realized using a ZZS (Zig-Zag Stacking) electrode assembly or an advanced Z-stacked (AZS) electrode assembly manufactured by folding a strip-type separator that is long in the length direction in a zigzag shape and inserting a unit electrode at the overlapping portion of the separator.

[0061] A separator according to one embodiment of the present disclosure may be used in an electrode assembly with improved stability and productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1a is a diagram of a conventional separator 1. The separator 1 may include a porous substrate 10 and a first porous coating layer 11 and a second porous coating layer 12 each present on each of two surfaces of the porous substrate. Figure 1a , the X direction represents the length direction of the separator 1 , the Y direction represents the width direction of the separator 1 , and the Z direction represents the thickness direction of the separator 1 .

[0063] Figure 1b 1 shows a cross section of a conventional separator 1 in the width direction. Specifically, Figure 1b A separator 1 having a first porous coating layer 11 and a second porous coating layer 12 on both surfaces of a porous substrate 10 without a thickness gradient is shown.

[0064] Figure 2a 2 is a diagram of an electrode assembly 2 assembled by an advanced Z-stack (AZS) or ZZS (zigzag stacking) method. Specifically, Figure 2a The structure of the electrode assembly 2 is shown, in which the separator 1 is folded in a zigzag shape, and the unit positive electrodes 21 and the unit negative electrodes 22 are arranged in an alternating manner at the folded and overlapped regions. Figure 2a , the X direction represents the width direction of the electrode assembly 2 , the Y direction represents the length direction of the electrode assembly 2 , and the Z direction represents the thickness direction of the electrode assembly 2 .

[0065] Figure 2b is a diagram of an electrode assembly 3 having a positive electrode tab 211 and a negative electrode tab 222, each at one of the two ends of an electrode assembly 2 including a stack of positive electrode / separator / electrode. Figure 2b , the X direction represents the width direction of the electrode assembly 2 , the Y direction represents the length direction of the electrode assembly 2 , and the Z direction represents the thickness direction of the electrode assembly 2 .

[0066] Figure 2c is a cross-sectional view of an electrode assembly 2 assembled by an AZS or ZZS method using a conventional separator 1 .

[0067] Figure 3a 1 is a diagram of a separator 1 according to an embodiment of the present disclosure. The total thickness of the separator 1 is kept constant based on the width direction of the separator 1, but the interfaces 111, 121 between the porous substrate 10 and the first and second porous coating layers 11, 12 have curved shapes convex toward the adjacent porous substrates, respectively.

[0068] Figure 3b is a diagram of a separator 1 according to one embodiment of the present disclosure. Figure 3b In FIG. 1 , the dotted line (1) indicates the center of the separator 1 in the width direction (Y).

[0069] Figure 3c is a diagram of a separator 1 according to one embodiment of the present disclosure. Figure 3c , the dotted line (m) indicates the center of the separator 1 in the thickness direction (Z).

[0070] Figure 4 A cross section of an electrode assembly 2 in a length direction (Y) is shown, the electrode assembly 2 being assembled by an AZS or ZZS method using the separator 1 according to one embodiment of the present disclosure.

[0071] Figure 5 is a diagram of a coating rod 4 for forming a porous coating layer according to one embodiment of the present disclosure.

[0072] Figure 6 is an image showing the evaluation result of the electrolyte wettability of the separator according to Comparative Example 1 of the present disclosure.

[0073] Figure 7 are images showing the evaluation results of the electrolyte wettability of the separator according to Example 1 of the present disclosure. DETAILED DESCRIPTION

[0074] Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings.

[0075] In the accompanying drawings, for convenience and clear description, the size of each element or a specific part of an element is enlarged, omitted or schematically shown. Therefore, the size of each element does not fully reflect the actual size. When it is determined that the detailed description of the relevant known function or element may unnecessarily obscure the subject matter of the present disclosure, the description is omitted. Hereinafter, the present disclosure will be described in detail.

[0076] It should be understood that when used in this specification, unless the context clearly indicates otherwise, “comprise” or “includes” indicates the presence of stated elements, but does not exclude the presence or addition of one or more other elements.

[0077] It should also be understood that when used in this specification, "A and / or B" means A or B, or both.

[0078] The terms used in the following detailed description are for convenience and are not intended to be limiting. The terms "upper", "lower", "left", "right", "front", "rear", "inner", and "outer" refer to directions in the drawings to which reference is made, or directions toward or away from the geometric center of the devices, systems, and elements described.

[0079] The present disclosure relates to a separator, an electrode assembly including the separator, and an electrochemical device including the electrode assembly. The electrochemical device may include, for example, a primary battery, a secondary battery, a supercapacitor, and a double-layer capacitor. More specifically, the secondary battery may be a lithium-ion secondary battery.

[0080] According to one aspect of the present disclosure, a separator for use in an electrochemical device is provided.

[0081] In the present specification, the separator may be presented in various shapes. For example, the separator may have a strip shape that is longer in the length direction than in the width direction. However, the present disclosure is not limited thereto.

[0082] In this manual, reference is made to Figure 1a The length direction, width direction and thickness direction of the separator 1 are described. Figure 1a , the X direction represents the length direction of the separator 1 , the Y direction represents the width direction of the separator 1 , and the Z direction represents the thickness direction of the separator 1 .

[0083] In one embodiment of the present disclosure, the separator 1 may have a strip shape with an aspect ratio of 1 or more, and in this case, the long side of the separator may exist in the length direction (X direction) and the short side may exist in the width direction (Y direction).

[0084] Referring to the drawings, a separator 1 according to an embodiment of the present disclosure includes a porous substrate 10 and a porous coating 11, 12 on at least one surface of the porous substrate. In this case, the separator may be characterized in that the thickness in the thickness direction (Z direction) remains constant over the entire separator along the length direction.

[0085] Reference Figure 2a In one embodiment of the present disclosure, the separator 1 can be used in a ZZS type electrode assembly or an advanced Z-stack (AZS) type electrode assembly, wherein the separator 1 is folded in a Z shape and the unit electrode is inserted at the overlapping portion of the separator 1, but the use of the present disclosure is not limited thereto.

[0086] Reference Figure 2b , which shows an electrode assembly 3, in which a separator 1 is folded in a Z-shape, unit electrodes 21, 22 are inserted at the folded and overlapped portion of the separator, and electrode tabs 221, 222 are formed at the ends of the unit electrodes.

[0087] In this manual, you can refer to Figure 2b Describe the length direction, width direction and thickness direction of the electrode assembly 3. Figure 2b , the X direction represents the width direction of the electrode assembly 2 , the Y direction represents the length direction of the electrode assembly 2 , and the Z direction represents the thickness direction of the electrode assembly 2 .

[0088] In one embodiment of the present disclosure, the electrode assembly to which the separator is applied has a positive electrode tab 211 or a negative electrode tab 222 (at each end of each electrode tab in the length direction), and can be applied to a battery that is long in the length direction. In addition, the positive electrode tab 211 and the negative electrode tab 222 can each be present at one or both ends in the same direction based on the length direction. However, the present disclosure is not limited thereto.

[0089] In one embodiment of the present disclosure, an electrode assembly using a separator has a ZZS or AZS type electrode assembly structure including a plurality of unit electrodes and separators between the unit electrodes, wherein the aspect ratio of the separator is 1 or greater, the separator is folded in a Z shape, and the unit electrodes are inserted at the overlapping portions of the separator.

[0090] A separator 1 according to one aspect of the present disclosure includes a porous substrate 10 and porous coating layers 11 , 12 containing inorganic particles, each on each of both surfaces of the porous substrate.

[0091] The porous substrate may include any type of substrate used for a separator without limitation, and will be described below.

[0092] The porous coating layer is a coating layer containing inorganic particles to improve the safety of the separator. Since the porous coating layer contains inorganic particles, the weight of the separator can be increased as the size of the separator increases (eg, the length of the separator increases).

[0093] The separator according to one aspect of the present disclosure includes a porous coating layer on each of the two surfaces of the porous substrate. In this case, in this specification, for the convenience of description, the porous coating layer on one surface of the porous substrate may be referred to as a "first porous coating layer 11", and the porous coating layer on the other surface of the porous substrate may be referred to as a "second porous coating layer 12".

[0094] Furthermore, in this specification, for convenience of description, the interface between the porous substrate and the first porous coating layer may be referred to as a “first interface 111 ”, and the interface between the porous substrate and the second porous coating layer may be referred to as a “second interface 121 ”.

[0095] In this specification, the "long side direction" of the separator refers to the direction on the side of the longer of the horizontal length and the vertical length of the separator. Specifically, the separator is a strip separator with an aspect ratio of 1 or more, more specifically, an aspect ratio greater than 1, and two or more unit electrodes are arranged on the separator. In this case, the long side direction indicates the direction in which the unit electrodes are arranged. Generally, the "long side direction" of the separator can match the direction in which the separator or the electrode assembly travels during the process of manufacturing the separator or the process of manufacturing the electrode assembly using the separator. With reference to the previous description, the length direction (X direction) of the separator 1 can be the long side direction.

[0096] In this specification, the "short side direction" of the separator refers to the direction on the shorter side of the horizontal length and the vertical length of the separator. Referring to the previous description, the width direction (Y direction) of the separator 1 can be the short side direction.

[0097] Figure 1b The side surface of the separator 1 in the width direction is shown, and the separator 1 has the first porous coating layer 11 and the second porous coating layer 12 , each on each of the two surfaces of the porous substrate 10 . Figure 1b The side surface of the separator 1 having an aspect ratio of 1 or more in the width direction is shown, and the porous coating layers 11 , 12 and the porous substrate 10 each have a uniform thickness in the width direction.

[0098] like Figure 1b As shown, in the case where the porous coating layer and the porous substrate each have a uniform thickness based on the width direction of the separator, when the electrode assembly formed by folding the separator is placed in a casing and the electrolyte is injected, it may not be possible to achieve sufficient wetting of the electrolyte deep in the central portion of the separator.

[0099] Reference Figure 2a and Figure 2c This problem may become more serious as the thickness of the electrode assembly increases, in other words, the number of stacked separators increases and the size of the separators increases (e.g., the length of the separators in the width direction and / or the length direction increases), resulting in deteriorated battery performance.

[0100] To solve this problem, the separator according to one aspect of the present disclosure has an aspect ratio of 1 or greater, the total thickness remains constant throughout the separator, and the interface between the porous substrate and each porous coating layer has a curved shape convex toward the porous substrate based on the width direction of the separator.

[0101] Figure 3a to Figure 3c 1 shows a side view of a separator 1 according to one aspect of the present disclosure. Specifically, the separator 1 has an aspect ratio of 1 or greater, and Figure 3a The side surface of the spacer in the width direction (Y direction) is shown.

[0102] Reference Figure 3a , the separator 1 has porous coating layers 11, 12, each on each of the two surfaces of the porous substrate 10. In this case, the interfaces 111, 121 between the porous substrate 10 and the porous coating layers 11, 12 respectively have curved shapes convex toward the porous substrate 10 based on the width direction of the separator.

[0103] Specifically, refer to Figure 3a , based on the width direction of the separator, the first interface 111 between the porous substrate 10 and the first porous coating layer 11 has a curved shape convex at the center portion toward the first porous substrate 10. In addition, based on the width direction of the separator, the second interface 121 between the porous substrate 10 and the second porous coating layer 12 has a curved shape convex at the center portion toward the porous substrate 10.

[0104] Therefore, the separator according to one aspect of the present disclosure may have a structure in which the thickness of the porous substrate gradually decreases to a minimum thickness from one end to the other end of the separator based on the width direction and then gradually increases.

[0105] According to one embodiment of the present disclosure, a porous substrate with a thickness gradient in the width direction as described above can be formed by adjusting the thickness adjusting screw of the extruder outlet when forming an extruded sheet in a method commonly used to manufacture a separator substrate. Specifically, the separator substrate can be manufactured by a common method after the polymer resin as a raw material is fed into the extruder and extruded via a T-die. In this case, the extruder can have a plurality of adjusting screws to adjust the thickness of the extruded product coming out of the T-die. By adjusting the screw so that when the polymer resin comes out of the T-die, the screw at the center of the T-die outlet is tighter and the screw at the two ends is not too tight, an extruded sheet with a smaller center thickness and a larger thickness at both ends in the width direction is formed. Subsequently, the extruded sheet can be cast and stretched in each of the width direction (TD) and the direction of travel (or length direction, MD) to manufacture a separator substrate with the above-mentioned shape. However, the present disclosure is not limited thereto.

[0106] Furthermore, the separator according to one aspect of the present disclosure may have a structure in which the thickness of the porous coating layer gradually increases to a maximum thickness from one end to the other end of the separator based on the width direction and then gradually decreases.

[0107] According to one embodiment of the present disclosure, on a porous substrate having a thickness gradient in the width direction as described above, in order to form a porous coating layer to keep the total thickness of the separator constant, a coating rod having different thicknesses according to positions can be used to form the porous coating layer. Specifically, Figure 5 is a diagram of a coating rod 4 for forming a porous coating according to one embodiment of the present disclosure. Figure 5 The separator having a constant total thickness can be manufactured by coating a slurry for forming a porous coating layer on at least one surface, preferably both surfaces, of the porous substrate using a coating rod having a greater thickness at the center portion than at both ends. However, the present disclosure is not limited thereto.

[0108] As described above, a separator according to one aspect of the present disclosure may have a structural feature in which the thickness of each of the porous substrate and the porous coating layer varies depending on the position in the width direction, and the total thickness of the separator, i.e., the sum of the thickness of the porous substrate and the thickness of the first porous coating layer and the second porous coating layer, remains constant.

[0109] In this specification, "the total thickness of the separator remains constant" means that the thickness value measured by the same method at any position within a certain area is within an error range of 5% or less. Specifically, when the difference between the thickness values ​​at two random positions within a certain area is 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, or 0% (i.e., no difference), the thickness can be said to remain constant.

[0110] In this specification, "gradual increase in thickness" means that the thickness value measured by the same method along a predetermined direction in a certain area increases continuously or discontinuously. The increase rate of the thickness value may be constantly maintained within an error range of 5% or less, and may vary discontinuously, but preferably, the gradual increase in thickness may mean that the thickness value increases continuously at a constant rate.

[0111] In this specification, "gradually decreasing thickness" means that the thickness value measured by the same method along a predetermined direction in a certain area decreases continuously or discontinuously. The reduction ratio of the thickness value may be constantly maintained within an error range of 5% or less, and may vary discontinuously, but preferably, the gradual decrease in thickness may mean that the thickness value decreases continuously at a constant ratio.

[0112] In this specification, unless otherwise specified, the "thickness" of each component may refer to a value measured using a thickness measuring tool generally used to measure the thickness of a separator of a battery. For example, the thickness measuring tool may be obtained from Mitutoyo VL-50S, but is not limited thereto.

[0113] In one embodiment of the present disclosure, the thickness of the porous substrate may be measured after removing the porous coating layer from the separator. For example, the thickness of the porous substrate remaining after removing the porous coating layer using a solvent that dissolves the porous coating layer included in the separator may be measured.

[0114] In one embodiment of the present disclosure, the thickness of the porous coating layer may be measured by measuring the thickness of the separator and subtracting the thickness of the porous substrate measured as described above from the thickness of the separator, but the measuring method is not limited thereto.

[0115] According to one embodiment of the present disclosure, the position where the thickness of the porous substrate is the minimum thickness, in other words, the position where the thickness of the porous coating is the maximum thickness, can be changed according to the poor wetting or non-wetting position of the electrolyte in the separator of the electrode assembly when the separator is used to manufacture the electrode assembly.

[0116] For example, when an electrode assembly is manufactured using a separator and placed in a shell, and then an electrolyte is injected, where the electrolyte is supplied at an equal density throughout the electrode assembly and the amount of electrolyte reaching the center portion of the separator is reduced, the position where the thickness of the porous coating is the maximum thickness can preferably be the center portion of the separator in the width direction.

[0117] In one embodiment of the present disclosure, when an electrode assembly is manufactured using a separator and placed in a shell, and then an electrolyte is injected, in a case where the amount of electrolyte reaching 1 / 3 of the electrode assembly in the length direction is reduced due to the shape of the shell, the position where the thickness of the porous coating is the maximum thickness can be 1 / 3 of the separator in the width direction.

[0118] According to one embodiment of the present disclosure, when an electrode assembly is manufactured using a separator and placed in a housing, and then an electrolyte is injected, the amount of electrolyte that reaches 1 / 2 of the electrode assembly in the length direction may generally decrease, and the thickness of the porous coating layer may be maximum at the center of the separator in the width direction. Specifically, the thickness of the porous coating layer may be maximum at 50% of the total length 100% in the width direction.

[0119] This may mean that the thickness of the porous coating layer is smallest at the outermost end of the separator in the width direction. Specifically, the thickness of the porous coating layer may be largest at 50% of 100% of the total length in the width direction.

[0120] In one embodiment of the present disclosure, the thickness of the porous substrate at the center of the separator, for example, 50% of the total width, can be 40% to 55% of the total thickness of the separator. For example, the thickness of the porous substrate at 50% of the total width of the separator can be 40% to 50% or 45% to 50% of the total thickness of the separator.

[0121] In one embodiment of the present disclosure, the thickness of the porous substrate at both ends of the separator, such as 0% or 100% of the total width, can be 50% to 70% of the total thickness of the separator. For example, the thickness of the porous substrate at 0% or 100% of the total width of the separator can be 55% to 65% or 60% of the total thickness of the separator.

[0122] In one embodiment of the present disclosure, the difference between the maximum thickness and the minimum thickness of the porous substrate in the separator may be 1 μm to 5 μm, 1.5 μm to 4 μm, or 2 μm to 3.5 μm, specifically 2 μm.

[0123] In one embodiment of the present disclosure, a thickness difference between a central portion and an end portion of the porous substrate may be 1 μm to 5 μm, 1.5 μm to 4 μm, or 2 μm to 3.5 μm, specifically 2 μm, based on a width direction of the separator.

[0124] According to one embodiment of the present disclosure, the curved shape of the interface between the porous substrate and the porous coating layer may be symmetrical with respect to the center of the separator in the width direction.

[0125] exist Figure 3b, in the side surface of the separator in the width direction according to one embodiment of the present disclosure, the center in the width direction is indicated by a dotted line (l).

[0126] Reference Figure 3b In the separator according to one embodiment of the present disclosure, the first interface between the porous substrate 10 and the first porous coating layer 11 may have a shape symmetrical with respect to the center (dashed line 1) in the width direction of the separator 1. In addition, the second interface between the porous substrate 10 and the second porous coating layer 12 may have a shape symmetrical with respect to the center (dashed line 1) in the width direction of the separator 1.

[0127] According to another embodiment of the present disclosure, the curved shapes of the two interfaces may be symmetrical with respect to the center of the separator in the thickness direction.

[0128] exist Figure 3c , in the side surface of the separator in the width direction according to one embodiment of the present disclosure, the center in the thickness direction is indicated by a dotted line (m).

[0129] Reference Figure 3c , the separator according to one embodiment of the present disclosure may have a curved shape of the first interface and a curved shape of the second interface that are symmetrical with respect to the center (dashed line m) of the separator 1 in the thickness direction.

[0130] According to another embodiment of the present disclosure, the separator may have a structure in which the curved shape of each of the first interface and the second interface is relative to the center in the width direction ( Figure 3b l) in the figure, and the curved shape of the first interface and the curved shape of the second interface are relative to the center in the thickness direction ( Figure 3c m) in is symmetrical.

[0131] According to one embodiment of the present disclosure, the partition may have a width relative to the center ( Figure 3b The structure is symmetrical about the dotted line 1 in the figure. Specifically, based on the center of the separator in the width direction, at random points spaced at equal distances from the center to both ends, the thickness of the porous substrate can be equal to each other, and the thickness of the porous coating can be equal to each other. More specifically, when the center position is 50% of the total length 100% of the separator in the width direction, the thickness of the porous substrate at 40% and the thickness of the porous substrate at 60% can be equal to each other. In addition, the thickness of the first porous coating at 40% and the thickness of the first porous coating at 60% can be equal to each other. In addition, the thickness of the second porous coating at 40% and the thickness of the second porous coating at 60% can be equal to each other.

[0132] According to one embodiment of the present disclosure, the porous coating layer on each of the two surfaces of the porous substrate may be oriented with respect to the center ( Figure 3c That is, the separator 1 may have a structure that is line-symmetrical with respect to the center in the thickness direction. Therefore, the thickness of the first porous coating layer and the second porous coating layer located on the same line in the separator thickness direction (Z direction) perpendicular to the separator width direction may be equal to each other.

[0133] In this specification, in view of errors in the manufacturing process or measurement errors as described above, "equal thickness" includes a thickness having a thickness difference of ±5% or less.

[0134] In one embodiment of the present disclosure, the thickness of the porous substrate may be, for example, 40% to 90% of the total thickness of the separator (100%). Specifically, the thickness of the porous substrate at the center portion may be 40% of the total thickness of the separator (100%), and in order to make the first interface and the second interface have a curved surface, as it moves toward both ends of the separator in the width direction, the thickness of the porous substrate may gradually increase and reach 90% at both ends of the separator in the width direction.

[0135] According to one embodiment of the present disclosure, when the thickness of the porous substrate is, for example, 40% to 90% of the total thickness of the separator, the thickness of each of the first and second porous coating layers may be 5% to 30% of the total thickness of the separator.

[0136] In another embodiment of the present disclosure, the thickness of the porous substrate can be, for example, 40% to 70% of the total thickness of the separator 100%. Specifically, the thickness of the porous substrate at both ends can be 50% to 70%, for example 60%, of the total thickness of the separator 100%, and in order to make the first interface and the second interface have a curved surface, as it moves toward the central part of the separator in the width direction, the thickness of the porous substrate can be gradually reduced and reach 40% to 60%, for example 40% to 55%, 40% to 50%, or 45% at the center of the separator in the width direction.

[0137] According to another embodiment of the present disclosure, when the thickness of the porous substrate is, for example, 40% to 70% of the total thickness of the separator (100%), the thickness of each of the first and second porous coating layers may be 15% to 30% of the total thickness of the separator (100%).

[0138] In one embodiment of the present disclosure, the separator may have a strip shape. Specifically, the strip separator may be a separator in a strip shape with a predetermined width, specifically, a separator in a rectangular shape with an aspect ratio of 1 or greater, specifically greater than 1. More specifically, the length of the long side of the separator may be 1.5m to 5m, specifically 1.8m to 4.8m.

[0139] Hereinafter, the porous substrate and the porous coating layer will be described by way of example. However, the separator according to one aspect of the present disclosure has the above-described novel shape and is not limited by the components of the porous substrate and the porous coating layer.

[0140] In one embodiment of the present disclosure, a porous substrate refers to a substrate having pores to act as a porous ion-conducting barrier that allows ions to pass through but prevents electrical contact between the negative electrode and the positive electrode. The pores are interconnected to allow gas or liquid to flow from one side of the substrate to the other.

[0141] In one embodiment of the present disclosure, the porous substrate may include a porous polymer film containing a thermoplastic resin for providing a shutdown function. Here, the shutdown function refers to a function in which when the temperature of the battery increases, the thermoplastic resin melts and the pores of the porous substrate are closed to block further ion transmission, thereby preventing thermal runaway in the battery.

[0142] In one embodiment of the present disclosure, the thermoplastic resin used in the porous substrate may preferably be a thermoplastic resin below 200°C. In addition, the thermoplastic resin may include, for example, those that can be used as a substrate for a separator, without limitation. For example, the thermoplastic resin may include polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylenenaphthalene or a mixture thereof, but is not limited thereto.

[0143] In one embodiment of the present disclosure, the porous substrate may be a polyolefin substrate.

[0144] In one embodiment of the present disclosure, when the thickness of the porous substrate satisfies the aforementioned range based on the total thickness of the separator, the thickness of the porous substrate is not limited to a specific range, but can be, for example, 5 μm to 300 μm, specifically 5 μm to 100 μm, 5 μm to 50 μm, 5 μm to 20 μm, 5 μm to 15 μm or 9 μm to 12 μm.

[0145] In one embodiment of the present disclosure, the porous coating layer comprises inorganic particles, and may further comprise a binder resin, and all or at least a portion of the surface of the inorganic particles may be coated with the binder resin. In this case, the inorganic particles are held together by surface bonding and / or point bonding via the binder resin. For example, the inorganic particles and the binder resin in the porous coating layer may be included in a weight ratio of 95:5 to 50:50. The porous coating layer has micropores therein so that the micropores are interconnected, and has a porous layer structure feature that allows gas or liquid to flow from one side to the other side.

[0146] In one embodiment of the present disclosure, the porous coating may have a pore structure derived from pores corresponding to the voids (interstitial volume) between inorganic particles. The pore size or porosity (volume ratio of pores) can be adjusted according to the particle size and particle size distribution. This structure can improve the tolerance to metal impurities present in the electrode and inhibit the shrinkage of the porous polyolefin substrate, thereby improving the safety of the electrochemical device.

[0147] In one embodiment of the present disclosure, the porous coating may include a plurality of nodes, the plurality of nodes including inorganic particles and a binder polymer covering at least a portion of the surface of the inorganic particles; and at least one filament, the at least one filament being formed in a linear form by the binder polymer of the nodes, wherein the filament has a node connection portion extending from one node and connecting the node to another node, and the node connection portion has a three-dimensional network structure formed by the interconnection of the filaments derived from the binder polymer.

[0148] In one embodiment of the present disclosure, as described above, the porous coating layer may be formed by a Safety Reinforced Separator (SRS) manufacturing method, a Ceramic Coated Separator (CCS) manufacturing method, or any other known manufacturing method, but is not limited thereto.

[0149] In one embodiment of the present disclosure, the inorganic particles are not limited to a specific type and may include those that are electrochemically stable. That is, the inorganic particles that can be used in the present disclosure are not limited to a specific type and may include those that are within the operating voltage range of the applied electrochemical device (e.g., relative to Li / Li + Those that do not undergo oxidation and / or reduction reactions within a range of 0 V to 5 V. Non-limiting examples of inorganic particles may include at least one of the following: BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1- x La x Zr 1-y Ti yO3(PLZT,0 <x<1,0<y<1)、Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3(PMN-PT), hafnium dioxide (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC or TiO2.

[0150] In one embodiment of the present disclosure, when the porous coating layer includes a binder resin, the binder resin may include, for example, a polyvinylidene fluoride-based resin (PVdF-based resin). In one embodiment of the present disclosure, the PVdF-based resin may include at least one of the following: a homopolymer of vinylidene fluoride (i.e., polyvinylidene fluoride), a copolymer of vinylidene fluoride and a monomer copolymerizable with vinylidene fluoride, or a mixture thereof. In one embodiment of the present disclosure, the monomer may include, for example, a fluorinated monomer and / or a chloride-based monomer. Non-limiting examples of fluorinated monomers can include at least one of the following: vinyl fluoride; trifluoroethylene (TrFE); chlorofluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD).

[0151] In one embodiment of the present disclosure, when the thickness of each porous coating satisfies the aforementioned ratio range based on the total thickness of the separator, the thickness of the porous coating is not limited to a specific range, but can be, for example, 0.5 μm to 50 μm, specifically 1 μm to 10 μm, 1.5 μm to 5 μm, 2 μm to 4 μm or 3 μm to 4 μm.

[0152] In one embodiment of the present disclosure, the first porous coating layer and the second porous coating layer may have the same composition, but may be formed in different compositions if necessary, and the present disclosure is not limited thereto.

[0153] Through the above structure, the separator according to one aspect of the present disclosure can improve the electrolyte wettability of the entire separator and has a beneficial effect in improving the performance of an electrochemical device using the separator, but the effects of the present disclosure are not limited thereto.

[0154] According to another aspect of the present disclosure, an electrode assembly using the above-mentioned separator is provided.

[0155] Specifically, refer to Figure 2a, the electrode assembly 2 has a structure in which the above-mentioned separator 1 is folded in a zigzag shape, and the unit positive electrodes 21 and the unit negative electrodes 22 are arranged in an alternating manner at a plurality of regions in which the separator is folded and overlapped.

[0156] An electrode assembly according to one embodiment of the present disclosure may include a unit positive electrode, a unit negative electrode, and a separator between the unit positive electrode and the unit negative electrode, wherein the unit positive electrode includes a plurality of unit positive electrodes arranged spaced apart from each other on one surface of the separator, the unit negative electrode includes a plurality of unit negative electrodes arranged spaced apart from each other on another surface of the separator, based on the long side direction of the separator, the position where the unit positive electrode is set and the position where the unit negative electrode is set do not overlap, and the separator is the above-mentioned separator.

[0157] Figure 4 A cross section of an electrode assembly 2 in a length direction (Y) according to one embodiment of the present disclosure is shown.

[0158] Reference Figure 4 , the electrode assembly 2 includes a separator 1 folded in a zigzag shape, and a plurality of unit positive electrodes 21 and a plurality of unit negative electrodes 22 arranged in an alternating manner at a plurality of regions where the separator is folded and overlapped.

[0159] According to one embodiment of the present disclosure, since the electrode assembly has a structure in which a plurality of unit electrodes are arranged on each of one surface and the other surface of a strip-type separator, the total length of the electrode assembly when unfolded can be, for example, 1m to 4.5m, specifically 1.2m to 4.3m.

[0160] As described above, the electrode assembly according to another aspect of the present disclosure has a long strip shape, but due to the unique structure of the separator, the electrolyte wettability of the central portion can be improved and the entire separator can be fully wetted by the electrolyte. Therefore, the electrolyte wettability of the long electrode assembly (or thick electrode assembly) can be improved, and the stability and productivity of the battery can be improved, but the effects of the present disclosure are not limited thereto.

[0161] In one embodiment of the present disclosure, the unit electrode may be a positive electrode and / or a negative electrode commonly used in an electrochemical device, and the positive electrode and the negative electrode may each include a current collector and an electrode active material coating on the current collector, and their size or shape is not limited to a specific size or shape.

[0162] In one embodiment of the present disclosure, when the electrode is the positive electrode, the positive electrode active material may include, for example, lithium transition metal oxides; lithium metal iron phosphate; lithium nickel-manganese-cobalt oxide; lithium nickel-manganese-cobalt oxide partially substituted with other transition metals; or two or more of them, but not limited thereto. Specifically, the positive electrode active material may include, for example, layered compounds such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; the chemical formula Li 1+x Mn 2-x O4 (x is from 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; Ni-site type lithium nickel oxides represented by the chemical formula LiNi 1-x M x O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01 to 0.3); lithium manganese composite oxides represented by the chemical formula LiMn 2-x M x O2 (M = Co, Ni, Fe, Cr, Zn or Ta, x = 0.01 to 0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); lithium metal phosphate LiMPO4 (M = Fe, Co, Ni or Mn); lithium nickel-manganese-cobalt oxide Li 1+x (Ni a Co b Mn c ) 1-x O2 (x = 0 to 0.03, a = 0.3 to 0.95, b = 0.01 to 0.35, c = 0.01 to 0.5, a + b + c = 1); lithium nickel-manganese-cobalt oxide partially substituted with aluminum Li a [Ni b Co c Mn d Al e 1-f M1 f O2 (M1 is at least one selected from Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P and S, 0.8 ≤ a ≤ 1.2, 0.5 ≤ b ≤ 0.99, 0 < c < 0.5, 0 < d < 0.5, 0.01 ≤ e ≤ 0.1, 0 ≤ f ≤ 0.1); lithium nickel-manganese-cobalt oxide partially substituted with other transition metals Li 1+x (Ni a Co b Mn c M d ) 1-x ​O2 (x = 0 to 0.03, a = 0.3 to 0.95, b = 0.01 to 0.35, c = 0.01 to 0.5, d = 0.001 to 0.03, a + b + c + d = 1, M is any one selected from Fe, V, Cr, Ti, W, Ta, Mg and Mo); disulfide compounds; Fe2(MoO4)3, but not limited to this.

[0163] In one embodiment of the present disclosure, when the electrode is a negative electrode, the negative electrode active material may include, for example, lithium metal or lithium alloy, soft carbon, hard carbon, natural graphite, crystalline graphite (Kish graphite), pyrolytic carbon, carbon fiber based on mesophase pitch, mesophase carbon microbeads, mesophase pitch, coke derived from petroleum or coal tar pitch, or a mixture thereof, but is not limited thereto.

[0164] In one embodiment of the present disclosure, the unit positive electrode and the unit negative electrode may each include an electrode tab at an end portion.

[0165] According to one embodiment of the present disclosure, the electrode tabs of the unit positive electrode and the unit negative electrode may be disposed at the same end in the length direction of the electrode assembly. Alternatively, the electrode tabs of the unit positive electrode and the unit negative electrode may be disposed at each of the two opposite ends in the length direction of the electrode assembly. The present disclosure is not limited thereto.

[0166] According to another aspect of the present disclosure, an electrochemical device including the electrode assembly and a case accommodating the electrode assembly may be provided.

[0167] In one embodiment of the present disclosure, the housing may include those commonly used as battery housings, and its shape is not particularly limited by battery use. For example, the housing may be a cylindrical shape using a can, a prismatic shape, a bag shape, or a coin shape.

[0168] When the electrode assembly is completed, the electrode assembly may be placed in a case by a common method of manufacturing an electrochemical device, followed by injecting an electrolyte and sealing the case. In this case, the electrochemical device may be, for example, a lithium secondary battery.

[0169] Hereinafter, the present disclosure will be described in more detail through embodiments, but the following description is provided to describe the present disclosure by way of example, and the scope of the present disclosure is not limited thereto.

[0170] [Manufacturing of separator]

[0171] The separators of Example 1 and Comparative Example 1 were manufactured as follows.

[0172] In this case, FIG. 2 shows the shape of the side surface of the separator of Example 1, and FIG. 1 shows the shape of the side surface of the separator of Comparative Example 1. In FIG.

[0173] Example 1

[0174] Fabrication of porous substrates

[0175] Three types of polyethylene polymers having different molecular weights, a polypropylene polymer, and an antioxidant are fed into an extruder at an appropriate ratio and mixed to form an extruded sheet through a T-die, followed by casting to form a polyolefin-based precursor film, and the polyolefin-based precursor film is stretched in each of the MD direction and the TD direction to obtain a porous substrate. In this case, the three types of polyethylene polymers used are PE 40 (Mw 400,000 g / mol), PE 90 (Mw 900,000 g / mol), and PE 150 (Mw 1,500,000 g / mol), and the polypropylene polymer is PP 35 (Mw 350,000 g / mol).

[0176] In addition, when the extruded sheet was formed through the T-die, the screw at the center portion of the T-die outlet was tighter, while the screws at both ends were less tight, so as to obtain an extruded sheet in a shape in which the center portion of the porous substrate in the width direction was thinner and the thickness increased toward both ends in a curved shape. The porosity of the porous substrate finally manufactured after stretching was 45% by volume.

[0177] The porous substrate was manufactured while adjusting the gap of the T-die so as to reduce the thickness in a curved shape convex from both ends to the center part toward the porous substrate so that the total width (short side, Y direction) was 500 mm, the length (long side, X direction) was 4 m, the thickness measured at each of the two ends of the short side was 9 μm, and the thickness at the center of the short side (i.e., the 250 mm position) was 7 μm.

[0178] Fabrication of porous coatings

[0179] PVDF-HFP binder (Mw 500,000 g / mol, HFP 15 wt %) and inorganic particles were added to a proper solvent at a weight ratio of 5:95 and mixed to prepare an inorganic coating slurry.

[0180] Use with Figure 5 The inorganic coating slurry thus prepared is applied to both surfaces of the porous substrate by a coating bar of the shape shown, and dried to form a porous coating layer on each of the upper and lower surfaces of the porous substrate.

[0181] The porous coating on each of the upper and lower surfaces was formed so that the thickness increased in a curved shape convex toward the porous substrate from both ends to the center (at a position of 250 mm) so that the thickness measured at each of the two ends of the short side was 3 μm and the thickness at the center was 4 μm.

[0182] Thus, a separator whose total thickness was kept constant at 15 μm over the entire separator was manufactured.

[0183] Comparative Example 1

[0184] Fabrication of porous substrates

[0185] A porous substrate was manufactured by the same method as in Example 1, except that the porous substrate had a constant thickness of 9 μm without thickness variation throughout the width direction (short side).

[0186] Fabrication of porous coatings

[0187] A porous coating layer was formed by the same method as in Example 1, except that the porous coating layer had a constant thickness of 3 μm without thickness variation throughout the width direction (short side).

[0188] Thus, a separator having a constant total thickness of 15 μm in the width direction was manufactured.

[0189] Table 1 summarizes the thickness of each component at both ends (0%, 100%) and the center (50%) based on 100% of the total length in the width direction of the separators thus prepared of Example 1 and Comparative Example 1.

[0190] [Table 1]

[0191]

[0192] [Evaluation of Separator Characteristics]

[0193] In order to evaluate electrolyte wetting and battery capacity by the following evaluation method, a battery was manufactured as follows.

[0194] The positive electrode active material (LiNi 0.8 Mn 0.1 Co 0.1 O2), a conductive material (carbon black), a dispersant and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a positive electrode active material layer, so that the concentration of the remaining components except water was 50% by weight. Subsequently, the slurry was applied to the surface of an aluminum foil (thickness 10 μm) and dried to manufacture a positive electrode with a positive electrode active material layer (thickness 120 μm).

[0195] Graphite (natural graphite / artificial graphite blend), conductive material (carbon black), dispersant and binder resin (mixture of PVDF-HFP and PVDF) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a negative electrode active material layer, so that the concentration of the remaining components except water was 50 wt %. Subsequently, the slurry was applied to the surface of a copper foil (thickness 10 μm) and dried to manufacture a negative electrode with a negative electrode active material layer (thickness 120 μm).

[0196] 19 positive electrode sheets and 20 negative electrode sheets manufactured as above were prepared, the separator manufactured as above was folded in a Z-shape, and the positive electrodes and the negative electrodes were inserted between the folded parts in an alternating manner and stacked to prepare a Z-folded electrode assembly.

[0197] Subsequently, the electrode assembly was placed in a pouch type case and injected with an electrolyte solution in which 1M LiPF6 was dissolved in a mixed solvent of 1,3-dioxolane:dimethoxyethane (DOL:DME 1:1 vol / vol), followed by aging and exhaust to manufacture a battery.

[0198] Electrolyte Wetting Evaluation

[0199] When the battery thus prepared was disassembled at SOC 60, Figure 6 is an image of the separator of Comparative Example 1, Figure 7 is an image of the separator of Example 1. In this case, each separator was observed with naked eyes by the difference in brightness of the electrolyte non-wetted region.

[0200] Initial Capacity Assessment

[0201] The battery was repeatedly charged and discharged for three cycles at a current of 0.33 C in a voltage range of 2.5 V to 4.3 V using an electrochemical charger / discharger, and then the capacity of the battery was measured. The results are shown in Table 2 below.

[0202] [Table 2]

[0203]

[0204] pass Figure 6 and Figure 7 From the results of Table 2, it is determined that the use of the separator according to one embodiment of the present disclosure can achieve good electrolyte wettability throughout the separator and obtain a further improved effect in achieving the theoretical capacity of the battery.

[0205] In particular, according to Figure 6 From the results of Table 2, it is determined that the uneven electrolyte wetting leads to a capacity lower than the theoretical capacity, and Comparative Example 1 has a significantly low initial capacity, while Figure 7From the results of Table 2, it was determined that uniform electrolyte wetting resulted in sufficient capacity compared to the theoretical capacity, and Example 1 had a significantly high initial capacity.

[0206] Although the present disclosure has been described above with reference to the embodiments and the accompanying drawings, it will be apparent to one of ordinary skill in the art to which the present disclosure pertains that various changes and modifications may be made within the scope of the present disclosure based on the foregoing description.

[0207] [reference numerals list]

[0208] 1: Separator

[0209] 10: Porous substrate

[0210] 11: First porous coating

[0211] 12: Second porous coating

[0212] 111: First interface

[0213] 121: Second interface

[0214] 2: Electrode assembly

[0215] 21: Unit positive electrode

[0216] 22: Unit negative pole

[0217] 211: Positive electrode tab

[0218] 222: Negative electrode tab

[0219] 3: Electrode assembly

[0220] 4: Coating rod

Claims

1. A separator, comprising: porous substrate; and a porous coating layer on each of the two surfaces of the porous substrate, the porous coating layer comprising inorganic particles, wherein the total thickness of the separator remains constant throughout the separator, wherein the aspect ratio of the partition is 1 or greater, and wherein an interface between each of the porous coating layers and the porous substrate has a curved shape convex toward the porous substrate based on a width direction of the separator. 2 . The separator according to claim 1 , wherein the porous substrate is thinnest at a center of the separator in the width direction. 3 . The separator according to claim 1 , wherein the porous substrate is thickest at an outermost end of the separator in the width direction. 4 . The separator according to claim 1 , wherein the curved shape of the interface between the porous substrate and the porous coating layer is symmetrical with respect to a center of the separator in the width direction. The separator according to claim 1 , wherein the curved shapes of the two interfaces are symmetrical with respect to a center of the separator in a thickness direction. The separator according to claim 1 , wherein the thickness of the porous substrate is 40% to 90% of 100% of the total thickness of the separator. 7 . The separator according to claim 1 , wherein the thickness of the porous substrate is 45% to 65% of 100% of the total thickness of the separator. 8 . The separator according to claim 1 , wherein at 50% of the total width of the separator, the thickness of the porous substrate is 40% to 55% of the total thickness of the separator. 9 . The separator according to claim 1 , wherein at 0% or 100% of the total width of the separator, the thickness of the porous substrate is 50% to 70% of the total thickness of the separator. 10 . The separator according to claim 1 , wherein the length of the separator in the length direction is 1.5 m to 5 m.

11. An electrode assembly, comprising: a positive electrode unit, a negative electrode unit, and a separator between the positive electrode unit and the negative electrode unit, wherein the separator is folded in a Z-shape, wherein the unit positive electrodes and the unit negative electrodes are arranged in an alternating manner at a plurality of regions where the separators are folded and overlapped, and The separator is as defined in any one of claims 1 to 10. 12 . The electrode assembly of claim 11 , wherein the unit positive electrode and the unit negative electrode each include an electrode tab at an end portion.

13. An electrochemical device comprising: The electrode assembly according to claim 11; and A casing for accommodating the electrode assembly.

14. The electrochemical device according to claim 13, wherein the electrochemical device is a lithium secondary battery. 15 . The electrochemical device according to claim 13 , wherein the case has a bag-type shape, a prism shape, a cylindrical shape, or a coin-type shape.

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