Secondary battery separator, electrode assembly comprising same, and method for manufacturing electrode assembly

Abstract

The present disclosure relates to a separator for a secondary battery, an electrode assembly comprising the same, and a method for manufacturing the electrode assembly, the separator for a secondary battery comprising: a porous base material layer; and a fusion layer that is laminated at a predetermined fusion thickness on at least one region of one or both surfaces of the porous base material layer and contains polymer particles having a glass transition temperature of 30 DEG C or more and 90 DEG C or less. According to the separator for the secondary battery, the electrode assembly comprising the same and the manufacturing method of the electrode assembly, the arrangement of the positive plate and the negative plate can be prevented from being staggered when the electrode assembly is assembled.

Description

Technical Field

[0001] The present disclosure relates to a separator for a secondary battery, an electrode assembly including the same, and a method of manufacturing the electrode assembly. More specifically, it relates to a separator for a secondary battery with improved heat resistance and weldability, an electrode assembly including the same, and a method of manufacturing the electrode assembly. Background Art

[0002] An electrode assembly disposed inside a secondary battery may include a positive electrode plate, a negative electrode plate, and a separator positioned between the positive electrode plate and the negative electrode plate. Recently, with the trend of high capacity and large area of secondary batteries, the size and number of the positive electrode plate and the negative electrode plate forming an electrode assembly have also increased.

[0003] However, as the size and number of the positive electrode plate and the negative electrode plate increase, areas where the positive electrode plate and the negative electrode plate do not adhere closely but warp occur during long-term charge and discharge, or the secondary battery expands and deforms (i.e., the swelling phenomenon), thus there is a problem of shortening the life of the secondary battery.

[0004] In addition, since the size and number of the positive electrode plate and the negative electrode plate increase, it is necessary to increase the assembly speed of the electrode assembly. However, when the assembly speed of the electrode assembly is increased, problems such as misalignment of the arrangement between the positive electrode plate and the negative electrode plate may occur due to vibration.

[0005] To solve the above problems, it is necessary to thermally weld the separator to suppress the shaking or deformation of the positive and negative electrodes. However, depending on the conditions of thermally welding the separator, there are problems such as a decrease in the performance of the separator or a long manufacturing time of the electrode assembly. Summary of the Invention

[0006] Technical Problems to be Solved

[0007] According to one aspect of the present disclosure, the technical problem to be solved is to prevent misalignment of the arrangement of the positive electrode plate and the negative electrode plate when assembling the electrode assembly.

[0008] According to another aspect of the present disclosure, the technical problem to be solved is to prevent misalignment of the arrangement of the positive electrode plate and the negative electrode plate without reducing the assembly speed of the electrode assembly.

[0009] According to still another aspect of the present disclosure, the technical problem to be solved is to prevent misalignment of the arrangement of a plurality of positive electrode plates and a plurality of negative electrode plates even when laminating a plurality of positive electrode plates and a plurality of negative electrode plates having a large area.

[0010] According to still another aspect of the present disclosure, the technical problem to be solved is to prevent a possible blocking phenomenon of the separator provided in a roll form while making it easy to thermally weld the separator.

[0011] According to another aspect of the present disclosure, the technical problem to be solved is that the performance of the separator does not deteriorate even after the hot melt bonding step.

[0012] According to another aspect of the present disclosure, the technical problem to be solved is to improve the production efficiency of the electrode assembly manufacturing process.

[0013] On the other hand, the separator for a secondary battery according to the present disclosure and a battery cell including the electrode assembly including the separator can be widely applied to electric vehicles, battery charging stations, energy storage systems (ESS), and other green technology fields such as photovoltaics and wind power that use batteries. In addition, the separator for a secondary battery according to the present disclosure and a battery cell including the electrode assembly including the separator can be applied to eco-friendly mobility tools such as electric vehicles and hybrid vehicles that suppress air pollution and greenhouse gas emissions to prevent climate change.

[0014] Means for Solving the Problem

[0015] To solve the above problems, the separator for a secondary battery according to the present disclosure may include: a porous substrate layer; and a welding layer laminated on at least one area of one or both sides of the porous substrate layer with a preset welding thickness, and including polymer particles having a glass transition temperature of 30 °C (Celsius temperature) or higher and 90 °C or lower.

[0016] The size of the polymer particles may be 0.1 μm (micrometer) or more and 0.7 μm or less.

[0017] The polymer particles may be any one of acrylate and copolymers of the acrylate or a combination thereof.

[0018] The welding thickness may be 1 μm (micrometer) or less.

[0019] The shape of the polymer particles may be heterogeneous.

[0020] In addition, the separator for a secondary battery according to the present disclosure may further include: a heat-resistant layer laminated on at least another area of one or both sides of the porous substrate layer with a preset heat-resistant thickness.

[0021] The heat-resistant layer may be laminated between the welding layer and the porous substrate layer in a region where the heat-resistant layer overlaps with the welding layer.

[0022] Relative to 100% by weight of the entire composition, the heat-resistant layer may include 60 to 99% by weight of inorganic particles and 40 to 1% by weight of a polymer binder.

[0023] The size of the inorganic particles may be 0.1 μm (micrometers) or more and 2.0 μm or less.

[0024] In addition, the electrode assembly according to the present disclosure includes: a first electrode; a second electrode, which is alternately laminated with the first electrode along a preset lamination direction and has an electrode polarity different from that of the first electrode; and a separator, which is located between the first electrode and the second electrode and on the outermost sides of the first electrode and the second electrode along the lamination direction, and includes a first portion that overlaps with the first electrode or the second electrode along the lamination direction and second portions formed on both sides of the first portion; the second portion may include a welding layer, and the welding layer includes polymer particles with a glass transition temperature of 30 °C (Celsius temperature) or more and 90 °C or less; at least a part of the second portion is joined to each other by heating the welding layer.

[0025] In addition, the difference between the positions of the first electrode and the second electrode before hot-welding the welding layer and the positions of the first electrode and the second electrode after joining the welding layer may be within a preset allowable error range.

[0026] The size of the polymer particles may be 0.1 μm (micrometers) or more and 0.7 μm or less.

[0027] The polymer particles may be any one of acrylate and copolymers of acrylate or a combination thereof.

[0028] The welding thickness, which is the laminated thickness of the welding layer, may be 1 μm (micrometers) or less.

[0029] There are multiple first portions, and the multiple first portions may be arranged at intervals from each other.

[0030] The first portion and the second portion may include: a porous substrate layer; and a heat-resistant layer laminated on one or both sides of the porous substrate layer with a preset heat-resistant thickness.

[0031] The heat-resistant layer may be laminated between the welding layer and the porous substrate layer.

[0032] In addition, the separator is folded into a zigzag shape, and the first electrode and the second electrode can be alternately arranged at each interval of the separator folded into the zigzag shape.

[0033] In addition, a method of manufacturing an electrode assembly according to the present disclosure includes: a step of alternately disposing a first electrode and a second electrode having an electrode polarity different from that of the first electrode between separators in a preset stacking direction; and a step of heat-bonding a second portion, which is another portion of the separator, located on both sides of a first portion that is a part of the separator, the first portion overlapping the first electrode and the second electrode in the stacking direction. In the step of heat-bonding the second portion, a welding layer including polymer particles having a glass transition temperature of 30 °C (Celsius temperature) or higher and 90 °C or lower stacked on the second portion can be heated at the glass transition temperature to be joined to each other. This can be referred to as thermal welding. Generally, thermal welding refers to joining different components together by applying pressure and heat.

[0034] Advantages of the Invention

[0035] According to one embodiment of the present disclosure, it is possible to prevent misalignment of the arrangement of the positive electrode plate and the negative electrode plate when assembling the electrode assembly.

[0036] According to another embodiment of the present disclosure, it is possible to prevent misalignment of the arrangement of the positive electrode plate and the negative electrode plate without reducing the assembly speed of the electrode assembly.

[0037] According to still another embodiment of the present disclosure, even when stacking a plurality of positive electrode plates and a plurality of negative electrode plates having a large area, it is possible to prevent misalignment of the arrangement of the plurality of positive electrode plates and the plurality of negative electrode plates.

[0038] According to still another embodiment of the present disclosure, it is possible to prevent a blocking phenomenon that may occur in a separator provided in a roll form.

[0039] According to still another embodiment of the present disclosure, the performance of the separator can be maintained even after the thermal welding step.

[0040] According to still another embodiment of the present disclosure, the production efficiency of the electrode assembly assembly process can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is an example of a battery cell including an electrode assembly according to the present disclosure;

[0042] Figure 2 Briefly shows a cross-section of an electrode assembly before pressurization and heating of an example of a separator according to the present disclosure;

[0043] Figure 3 Briefly shown is a cross-section of an electrode assembly after heating an example of a separator according to the present disclosure;

[0044] Figure 4 Briefly shown is a cross-section of another example of an electrode assembly before heating a separator according to the present disclosure;

[0045] Figure 5 Briefly shown is a cross-section of another example of an electrode assembly after heating a separator according to the present disclosure;

[0046] Figure 6 is an example of a separator according to the present disclosure;

[0047] Figure 7 is a cross-section of a separator according to the present disclosure;

[0048] Figure 8 is an example of a jig or a pressurizing and heating device for manufacturing an electrode assembly according to the present disclosure.

[0049] Description of Reference Numerals

[0050] 10: Electrode assembly

[0051] 11: First electrode

[0052] 15: Second electrode

[0053] 17: Separator

[0054] 171: First part

[0055] 172: Second part

[0056] 179: Porous substrate layer

[0057] 100: Battery cell Detailed Description of the Invention

[0058] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The configurations or control methods of the devices described below are only for illustrating the embodiments of the present disclosure and are not intended to limit the scope of the rights of the present disclosure. The same reference numerals are used throughout the specification to denote the same components.

[0059] The specific terms used in this specification are only for the convenience of description and are not used as limitations of the exemplary embodiments.

[0060] For example, expressions such as "identical" and "the same" not only represent a state of being exactly the same in a strict sense but also represent a state in which there are tolerances or differences in the degree of achieving the same function.

[0061] For example, expressions indicating relative or absolute configurations such as "in a certain direction", "along a certain direction", "parallel", "perpendicular", "centered on ~", "concentric", or "coaxial" not only represent the exact configurations as such, but also include states with tolerances or angular or distance relative displacements to achieve the same function.

[0062] Terms preceded by expressions such as "first", "second", "third", etc. attached to the constituent elements mentioned below are used to avoid confusion of the so-called constituent elements and have nothing to do with the order, importance, or primary-secondary relationship between the constituent elements. For example, an invention that only includes a second constituent element without a first constituent element can also be realized.

[0063] In the present specification, singular expressions include plural expressions, unless otherwise clearly indicated in the context.

[0064] Figure 1 is an example of a battery cell including an electrode assembly according to the present disclosure.

[0065] See Figure 1 , the battery cell 100 according to the present disclosure may include an electrode assembly 10, a housing 113 that internally houses the electrode assembly 10, and lead electrode tabs 111, 112 that are electrically connected to the electrode assembly 10 and protrude outward from the housing 113.

[0066] The electrode assembly 10 may include a first electrode 11 (see Figure 2 ), a second electrode 15 having an electrode polarity different from that of the first electrode (see Figure 2 ), and a separator 17 for electrically isolating the first electrode 11 and the second electrode 15 from the outside or other electrodes (see Figure 2 ).

[0067] The first electrode 11 is one of the positive electrode and the negative electrode, and the second electrode 15 is the other of the positive electrode and the negative electrode.

[0068] The housing 113 may form a receiving space 120 for housing the electrode assembly 10. The receiving space 120 may house the electrode assembly 10 and an electrolyte (not shown in the figure). The housing 113 may be formed by folding a sheet-shaped outer packaging material to form the receiving space 120.

[0069] Specifically, the outer case 113 may include a first outer packaging material 113a forming a first accommodation space and a second outer packaging material 113b forming a second accommodation space disposed corresponding to the first accommodation space. The first outer packaging material 113a and the second outer packaging material 113b may be integrally formed. When the first outer packaging material 113a and the second outer packaging material 113b are folded towards each other, the openings of the first accommodation space and the second accommodation space may be combined into one to form an accommodation space 120.

[0070] On the other hand, the first outer packaging material 113a and the second outer packaging material 113b may be combined and sealed with each other to prevent leakage of the electrolyte accommodated therein. The first outer packaging material 113a may include a first peripheral portion formed around the first accommodation space, and the second outer packaging material 113b may include a second peripheral portion formed around the second accommodation space. And, the first peripheral portion and the second peripheral portion may be hermetically joined to each other.

[0071] On the other hand, the battery cell 100 may include lead electrode tabs 111, 112 for electrically connecting the electrode assembly 10 to the outside. Inevitably, the lead electrode tabs 111, 112 need to protrude to the outside of the outer case 113. Therefore, in consideration of this, the first outer packaging material 113a or the second outer packaging material 113b may further include lead grooves 114a, 114b corresponding to the shapes of the lead electrode tabs 111, 112. At least a part of the lead electrode tabs 111, 112 is inserted into the lead grooves 114a, 114b, so that the first outer packaging material 113a and the second outer packaging material 113b can be combined with each other without significant deformation caused by the lead electrode tabs 111, 112.

[0072] Figure 1 The electrode assembly 10 accommodated in the pouch-type battery cell 100 is shown as an example, but the electrode assembly 10 according to the present disclosure can be applied not only to pouch-type battery cells but also to prismatic and cylindrical battery cells.

[0073] Figure 2 Briefly shown is a cross-section of the electrode assembly before pressurization and heating of an example of the separator according to the present disclosure.

[0074] More specifically, Figure 2 Shown is Figure 1 a cross-section of the electrode assembly 10 cut along the A-A' direction. Referring to Figure 2 , the electrode assembly 10 may include a first electrode 11, a second electrode 15, and a separator 17.

[0075] The first electrode 11 and the second electrode 15 may be formed by stacking a positive electrode active material or a negative electrode active material on an electrode plate made of a metal material. The electrode plate may include a coating portion as a portion where the positive electrode active material or the negative electrode active material is stacked and a non-coating portion 119, 159 protruding from one side of the coating portion (see Figure 6 ).

[0076] The first electrodes 11 and the second electrodes 15 may be alternately stacked along a preset stacking direction.

[0077] The electrode assembly 10 may include a separator 17 to prevent the first electrode 11 and the second electrode 15 from directly contacting each other. Also, the separator 17 may be located at the outermost side of the electrode assembly 10 along the stacking direction to prevent the electrode assembly 10 from directly contacting the housing 113 .

[0078] See also Figure 2 In order to be arranged between the first electrode 11 and the second electrode 15 and / or arranged at the outermost side of the electrode assembly 10 along the stacking direction, a separator 17 can be folded into a zigzag shape.

[0079] That is, the electrode assembly 10 may be formed by inserting the first electrode 11 and / or the second electrode 15 between the folded parts of the separator 17. To this end, the separator 17 may be provided in a zigzag shape. Therefore, the first electrode 11 and the second electrode 15 may be inserted between the separators 17 from opposite directions via the separator 17 folded in the zigzag shape.

[0080] On the other hand, the diaphragm 17 may include a first portion 171 (see Figure 3 ) and Part II, 172 (see Figure 3 ), the first portion 171 is a portion overlapping with the first electrode 11 and / or the second electrode 15 along the stacking direction, and the second portion 172 is a portion not overlapping with the first electrode 11 and / or the second electrode 15.

[0081] See also Figure 2 When the diaphragm 17 is folded into a zigzag shape, the second portion 172 may be disposed on both sides of the first electrode 11 and / or the second electrode 15 along the stacking direction.

[0082] That is, when the separator 17 folded into the zigzag shape is orthographically projected onto an imaginary plane along the stacking direction, the area of ​​the orthographic projection may be larger than the area of ​​the first electrode 11 and / or the second electrode 15. Figure 2It can be seen that in a cross-section of the electrode assembly 10, the length W1 of the separator 17 folded into the sawtooth form is greater than the length of the first electrode 11 and / or the second electrode 15.

[0083] That is, a part of the area of the separator 17 disposed facing the first electrode 11 and / or the second electrode 15 is larger than the first electrode 11 and / or the second electrode 15, so there may be a remaining portion M that does not overlap with the first electrode 11 and / or the second electrode 15.

[0084] The remaining portion M can be located on both sides in a direction perpendicular to the stacking direction of the electrode assembly 10. And the remaining portion M can be a portion corresponding to the second portion 172 in the separator 17 folded into the sawtooth form.

[0085] Figure 3 Briefly shown is a cross-section of an electrode assembly after heating an example of the separator according to the present disclosure.

[0086] See Figure 3 , at least a part of the second portion 172 corresponding to the remaining portion M in the electrode assembly 10 according to the present disclosure can be joined.

[0087] The second portions 172 can be joined to each other by heat welding. Therefore, by restricting the movement of the first electrode 11 and / or the second electrode 15, the misalignment of the arrangement of the first electrode 11 and / or the second electrode 15 caused by the movement of the electrode assembly 10 or the vibration during manufacturing can be reduced. In addition, even if the manufacturing speed of the electrode assembly 10 is increased, the misalignment of the arrangement of the first electrode 11 and / or the second electrode 15 can be reduced.

[0088] In order to join the second portions 172 in the electrode assembly 10 according to the present disclosure to each other, the second portions 172 in the separator 17 can include a welding layer 177 (see Figure 7 ).

[0089] That is, the difference between the positions of the first electrode 11 and the second electrode 15 laminated before heat welding the welding layer 177 and the positions of the first electrode 11 and the second electrode 15 after heat welding (or joining) the welding layer 177 can be within a preset allowable error range. The welding layer 177 will be described below.

[0090] Figure 4 Briefly shown is a cross-section of another example of an electrode assembly before heating the separator according to the present disclosure.

[0091] With Figure 2 And Figure 3As shown, a separator 17 is folded into a different zigzag pattern. Refer to Figure 4 According to another embodiment of the present disclosure, the separator 17 is not integrally formed but may have a plurality of separators. The plurality of separators 17 may be respectively disposed between the first electrode 11 and / or the second electrode 15 along the stacking direction, or disposed outside the electrode assembly 10 along the stacking direction.

[0092] Refer to Figure 4 As shown, each of the plurality of separators 17 may include a first portion 171 that overlaps with the first electrode 11 and / or the second electrode 15 along the stacking direction (refer to Figure 5 ), and a second portion 172 located on both sides of the first portion 171 and thus not overlapping with the first electrode 11 and / or the second electrode 15 (refer to Figure 5 ).

[0093] That is, since the area of each separator 17 is larger than that of the first electrode 11 and / or the second electrode 15, the second portion 172 can be arranged not to overlap with the first electrode 11 and / or the second electrode 15. The second portion 172 may also be referred to as a surplus portion M of the separator 17. Refer to Figure 4 It can be seen that in a cross-section of the electrode assembly 10, the length W2 of the separator 17 is greater than the length of the first electrode 11 and / or the second electrode 15.

[0094] The surplus portion M may be located on both sides in a direction perpendicular to the stacking direction. In addition, the surplus portion M may be a portion corresponding to the second portion 172 of each separator 17 stacked along the stacking direction.

[0095] Figure 5 Briefly shown is a cross-section of an electrode assembly after heating another example of the separator according to the present disclosure.

[0096] Refer to Figure 4 and Figure 5 In the electrode assembly 10 according to the present disclosure, at least a part of the second portion 172 corresponding to the surplus portion M may be joined to each other by hot melting.

[0097] That is, by the hot melting, the movement of the first electrode 11 and / or the second electrode 15 is restricted, so that the misalignment of the arrangement of the first electrode 11 and / or the second electrode 15 caused by the movement of the electrode assembly 10 or the vibration during manufacturing can be reduced. In addition, even if the manufacturing speed of the electrode assembly 10 is increased, the misalignment of the arrangement of the first electrode 11 and / or the second electrode 15 can be reduced.

[0098] Figure 3 andFigure 5 It shows that there is no gap between the second part 172 and the sides of the first electrode 11 and / or the second electrode 15 when the second parts 172 in the diaphragm 17 are joined to each other. However, as long as the diaphragm 17 can restrict the movement of the first electrode 11 and / or the second electrode 15, it is also acceptable if a certain degree of gap is generated between the second part 172 and the sides of the first electrode 11 and / or the second electrode 15 when the second part 172 is joined.

[0099] On the other hand, referring to Figures 2 to 5 , it shows a method of folding one diaphragm in the electrode assembly 10 into a zigzag shape or forming the electrode assembly 10 using a plurality of independent diaphragms.

[0100] However, the method of manufacturing the electrode assembly 10 is not limited to this. For example, the electrode assembly 10 can be formed by winding a positive electrode and a negative electrode separately arranged and wrapped by the diaphragm 17 into a roll shape. An electrode assembly in this form can be called a "Jelly Roll".

[0101] As long as the diaphragm 17 can include a second part 172 that forms a margin part M on both sides of the first electrode 11, the electrode assembly 10 can be formed into any shape.

[0102] Figure 6 is an example of the diaphragm according to the present disclosure.

[0103] More specifically, Figure 6 it shows an example of unfolding the diaphragm 17 in a zigzag shape.

[0104] Referring to Figure 6 , when the diaphragm 17 folded into the zigzag shape is unfolded again, the diaphragm 17 has a plurality of the first parts 171, and the second parts 172 can be located on both sides of the first parts 171. Therefore, the plurality of first parts 171 can be arranged at a preset interval.

[0105] For easy understanding, in Figure 6 , the first electrode 11 and the second electrode 15 are only shown in a brief form with dashed lines. Therefore, in Figure 6 , the uncoated part 119 of the first electrode 11 and the uncoated part 159 of the second electrode are shown with dashed lines. And, the area A1 occupied by the coated part of the first electrode 11 and / or the second electrode 15 is shown. In addition, the area A2 corresponding to the margin part M (refer to Figure 2 or Figure 4 ) which is the part of the diaphragm 17 that does not overlap with the first electrode 11 and / or the second electrode 15 is also briefly shown.

[0106] For the sake of brief description, the area A1 occupied by the coated portion of the first electrode 11 and / or the second electrode 15 is illustrated to be the same as the area of the first portion 171, but the area of the area A1 occupied by the coated portion of the first electrode 11 and / or the second electrode 15 may also be smaller than the area of the first portion 171. The area A2 corresponding to the surplus portion M is also illustrated to be the same as the area of the second portion 172, but this is just an example.

[0107] Preferably, the sizes of the second portions 172 arranged on both sides of the first portion 171 may be the same.

[0108] That is, the lengths L1 of the second portions 172 located on both sides of the first portion 171 may all be the same.

[0109] Referring to Figure 6 it can be seen that when the separator 17 folded into the sawtooth form is unfolded again, the plurality of first portions 171 are arranged at intervals of a length L2 equivalent to twice the length L1 of the second portion 172. This is because a surplus portion M needs to be provided on both sides of the first electrode 11 and / or the second electrode 15 when folding the separator 17. Therefore, the first portions 171 closest to the two ends 175 and 176 of the separator 17 in the X direction may be arranged at a distance equivalent to the length L1 of the second portion 172 from the two ends of the separator 17.

[0110] The separator 17 may further include virtual folding lines 173 between the respective first portions 171 among the plurality of first portions 171. The folding lines 173 may be arranged at the same distance from any one of the first portions 171 and another first portion 171 adjacent to any one of the first portions 171.

[0111] When the separator 17 is folded into a sawtooth form with the folding line 173 as the center, second portions 172 of the same size are arranged on both sides of the first portion 171. The first portion 171 overlaps with the first electrode 11 and / or the second electrode 15 in the stacking direction (i.e., the direction perpendicular to the X direction and the Y direction). On the contrary, the second portion 172 does not overlap with the first electrode 11 and / or the second electrode 15.

[0112] Therefore, referring to Figure 3 , when the second portions 172 are joined to each other, the joined second portions 172 restrict the movement of the first electrode 11 and / or the second electrode 15, thereby being able to minimize the misalignment of the arrangement of the first electrode 11 and / or the second electrode 15 in the X direction.

[0113] Figure 7This is a cross-section of a separator according to the present disclosure.

[0114] See Figure 7 , the separator 17 may include a porous substrate layer 179. The porous substrate layer 179 may be made of a material that prevents the first electrode 11 and the second electrode 15 from contacting while allowing ions to pass through. Generally, the porous substrate layer 179 may be formed of a polyolefin (PO) series material such as polyethylene (PE) and polypropylene (PP) having electrochemical stability and appropriate mechanical strength.

[0115] That is, the polyolefin series material may be selected from one or more of polyethylene, polypropylene, and their copolymers, but is not limited thereto.

[0116] In addition, the porous substrate layer 179 is in the form of a thin film or membrane having a thickness of 5 to 30 μm (micrometers), and the thin film may include micropores. In addition, the thin film may be made after being repeatedly stretched (elongated or stretched).

[0117] On the other hand, the separator 17 according to the present disclosure may include a heat-resistant layer 178 laminated on one or both sides of the porous substrate layer 179 to improve the heat resistance of the separator 17.

[0118] In addition, the heat-resistant layer 178 may be laminated between the welding layer 177 and the porous substrate layer 179. More specifically, the heat-resistant layer 178 may be laminated to overlap the welding layer 177.

[0119] Figure 7 For illustration, an example is shown in which the heat-resistant layer 178 and the welding layer 177 are only coated on one side of the porous substrate layer 179, but the heat-resistant layer 178 and the welding layer 177 may be coated on both sides of the porous substrate layer 179 differently.

[0120] Generally, the tensile strength of the porous substrate layer 179 is 500 kgf / cm² or more in all directions. In order to uniformly improve the strength in all directions, it can be manufactured by biaxial stretching in the X direction (see Figure 6 ) and the Y direction (see Figure 6 ) rather than uniaxial stretching. The separator 17 manufactured by repeated stretching has the advantage that the tensile strength increases in the stretching direction, but since there is a stress to shrink in the stretching direction, there may be a disadvantage of shrinking when the temperature rises.

[0121] To solve this problem, the separator 17 according to the present disclosure may include a heat-resistant layer 178 laminated (or coated) on one or both sides of the porous substrate layer 179 with a preset heat-resistant thickness.

[0122] That is, the separator 17 according to the present disclosure may include the heat-resistant layer 178 in contact with the first electrode 11 and / or the second electrode 15 at least on the porous substrate layer 179 of the first part 171.

[0123] In addition, the separator 17 according to the present disclosure may include the heat-resistant layer 178 located on one or both sides of the porous substrate layer 179 in the entire area including not only the first part 171 but also the second part 172.

[0124] The heat-resistant layer 178 may include inorganic particles and a binder (or polymer binder) for binding the inorganic particles. With respect to 100% by weight of the mixture (or entire composition) including inorganic particles and the polymer binder, the content of the inorganic particles in the heat-resistant layer 178 may be 60 to 99% by weight. In addition, with respect to 100% by weight of the entire composition, the content of the binder in the heat-resistant layer 178 may be 40 to 1% by weight.

[0125] This is because when the content of the inorganic particles is less than 60% by weight, the voids formed between the inorganic particles decrease due to the excessive content of the binder, and thus the pore diameter and porosity decrease, which may lead to a decline in the performance of the battery cell. On the contrary, when the content of the inorganic particles exceeds 99% by weight, the adhesion force between the inorganic substances weakens due to the insufficient content of the binder, which may lead to a decline in the mechanical properties of the separator 17.

[0126] The size of the inorganic particles included in the heat-resistant layer 178 may be 0.1 μm (micrometer) or more and 2 μm or less.

[0127] A particle size analyzer that measures the particle size by laser diffraction method may be used to measure the size of the inorganic particles. The measured particle size will exhibit a statistically specific distribution according to the size, and the median value (D50) may be defined as the size of the inorganic particles.

[0128] As another measurement method, a measurement method related to the size of the inorganic particles may also be performed according to ASTM E3340.

[0129] And, the heat-resistant thickness may be 1 μm or more and 10 μm or less.

[0130] In this specification, the heat-resistant thickness and / or the following welding thickness refer to the thickness of the heat-resistant layer 178 and / or the welding layer 177 laminated or coated. It can be calculated by laminating the heat-resistant layer 178 and / or the welding layer 177 on the porous substrate layer 179 and measuring the thickness (referred to as the total thickness) and then subtracting the thickness of the porous substrate layer 179. That is, the heat-resistant thickness or the welding thickness can be calculated by calculating the difference between the total thickness and the known thickness of the porous substrate layer 179.

[0131] For this purpose, a contact thickness gauge can be used to measure the thickness of the separator 17 (i.e., the thickness of the porous substrate layer 179 coated with the heat-resistant layer 178 and / or the welding layer 177 or the total thickness). Specifically, the separator is placed on a flat support surface and then the tip is brought into contact with the separator 17 under a certain pressure for measurement.

[0132] As another measurement method, the measurement method for the separator (or film) can be performed according to ASTM D6988.

[0133] Preferably, the inorganic particles can be materials that are chemically and electrochemically stable. For this purpose, the inorganic particles can be any one or a combination of aluminum oxides such as alumina and boehmite, barium titanium oxide, titanium oxide, magnesium oxide, clay, and glass powder.

[0134] On the other hand, the separator 17 according to the present disclosure may include a welding layer 177 formed with a preset welding thickness for the joining between the separators 17.

[0135] The separator 17 according to the present disclosure may include a welding layer 177 formed on one or both sides of the porous substrate layer 179 with a preset welding thickness at least in the second part 172.

[0136] Similar to the heat-resistant layer 178, the welding layer 177 can be formed on one or both sides of the porous substrate layer 179 in the entire area of the separator 17 including not only the first part 171 but also the second part 172 in the separator 17.

[0137] Preferably, the welding layer 177 can be formed on the outermost layer of the separator 17. For example, when one side of the separator 17 includes the heat-resistant layer 178, the heat-resistant layer 178 can be laminated on the porous substrate layer 179 first and then the welding layer 177 can be laminated on the heat-resistant layer 178.

[0138] That is, based on the porous substrate layer 179, the welding layer 177 can be disposed farther than the heat-resistant layer 178.

[0139] The heat-resistant layer 178 and the welding layer 177 can be coatings laminated on the porous substrate layer 179.

[0140] As described above, at least a part of the second portion 172 includes the welding layer 177 for bonding between the separators 17. That is, a general separator welds the electrode plate to the separator, or bonds the uncoated or laminated porous substrate layer 179, while the welding layer 177 can bond the coated or laminated porous substrate layer 179 (hereinafter referred to as a composite separator).

[0141] By joining the composite separators through the welding layer 177, the composite separators can be bonded (or welded) under relatively improved welding conditions, that is, at a relatively low temperature, low pressure, and short time.

[0142] For the method of bonding an electrode to a separator as a general method, since the surface of the negative electrode is smooth and there is no additional bonding substance, a bonding layer containing a polymer substance with a high adhesive force at a relatively high glass transition temperature is required. Alternatively, in order to bond an electrode (especially a negative electrode with a relatively smooth surface) to a separator, the general separator may also require a polymer substance with a high adhesive force at a very low glass transition temperature.

[0143] However, for the separator 17 according to the present disclosure, since the separators 17 to be joined to each other all include the welding layer 177, compared with the general method, the welding layer 177 can bond the second portions 172 to each other at a relatively low glass transition temperature, at a low pressure, and in a short time.

[0144] The bonding (or welding) can be achieved by a method called hot welding. For this purpose, the welding layer 177 can contain polymer particles with a glass transition temperature of 30 °C (degrees Celsius) or higher and 90 °C or lower. That is, within the range of the glass transition temperature, the polymer particles can cause the second portions 172 to bond to each other.

[0145] For this purpose, the polymer particles contained in the welding layer 177 can be a polymer adhesive (or a polymer adhesive made of a polymer material). The polymer adhesives can combine with each other at a temperature above the glass transition temperature.

[0146] If polymer particles with a relatively low glass transition temperature are used (for example, if the glass transition temperature at which hot melt bonding occurs is lower than 30°C), it is easy to ensure the adhesive force, but a blocking phenomenon may occur where the separators adhere to each other in a wound roll form before the electrode assembly 10 is assembled. In addition, if polymer particles with a relatively high glass transition temperature are used (for example, if the glass transition temperature is higher than 90°C), it may be difficult to ensure the adhesive force.

[0147] In addition, when relatively low temperature and low pressure are employed, it is possible to minimize the decrease in the transmittance of the separator 17 after welding and the resulting increase in the resistance of the battery cell. In addition, when using a relatively short time, it is possible to minimize the increase in the battery cell assembly time caused by the welding.

[0148] The welding layer 177 may include polymer particles. The shape of the polymer particles may be heterogeneous. And the size of the polymer particles is preferably 0.1 μm (micrometer) or more and 0.7 μm or less.

[0149] This is because when the size of the polymer particles is less than 0.1 μm, it is difficult to handle due to their relative fineness, and a relatively large amount of coating is required to achieve the adhesive force. In addition, when the size of the polymer particles exceeds 0.7 μm, the welding thickness of the welding layer 177 may become thick. Because if the thickness of the welding layer 177 is too thick, the ion migration distance through the welding layer 177 increases, which may lead to an increase in resistance.

[0150] Preferably, in the separator 17 according to the present disclosure, the welding thickness may be 1 μm (micrometer) or less.

[0151] On the other hand, the method of forming the separator 17 and the electrode assembly 10 according to the present disclosure is self-evident to those of ordinary skill in the art, and thus is not particularly limited.

[0152] In particular, the heat-resistant layer 178 may be coated or laminated on the porous substrate layer 179 by a gravure coating method, and the welding layer 177 may be coated or laminated on the porous substrate layer 179 by a bar coating or spray coating method.

[0153] The polymer particles may include a polymer material composed of acrylate and its copolymer having a glass transition temperature of 30 °C (degrees Celsius) or higher and 90 °C or lower. Because if the glass transition temperature is lower than 30 °C, the pores of the heat-resistant layer 178 or the porous substrate layer are blocked during welding, resulting in a serious decrease in the permeability of the separator 17, and thus the life of the battery cell may be reduced. In addition, because if the glass transition temperature exceeds 90 °C, the welding force cannot be exhibited under general hot welding temperature conditions.

[0154] On the other hand, Figure 2 and Figure 6 Taking the separator 17 folded in a zigzag shape as an example has been described. On the contrary, Figure 4 The illustrated electrode assembly 10 shows an example including a plurality of separators 17 stacked in the stacking direction. However, the description of the heat-resistant layer 178 and the welding layer 177 formed on the first part 171 and the second parts 172 located on both sides of the one first part 171 is the same as that of Figure 6 and is thus omitted.

[0155] The following describes examples and comparative examples related to the welding layer 177.

[0156] Examples 1 to 3

[0157] (1) Selection of the porous substrate layer

[0158] A polyolefin-based microporous membrane is used as the porous substrate layer 179. Specifically, a separator for a secondary battery with a thickness of 9 μm composed of a single layer of polyethylene is used.

[0159] (2) Manufacturing process of laminating (or coating) the heat-resistant layer 178 on the porous substrate layer

[0160] After adding 3 g of an inorganic dispersant and 231 g of boehmite (average particle size 0.7 μm, KC Corporation) to 150 g of water (DI-water) and uniformly dispersing them, 14 g of a polyacrylate-based copolymer polymer binder (Tg 155 °C, Zeon Corporation, Japan) was added to prepare a slurry for coating the heat-resistant layer.

[0161] (3) Preparation process of the solution for coating the welding layer 177.

[0162] For Example 1, 20 g of a polyacrylate-based copolymer polymer binder (Tg 45 °C, Zeon Corporation, Japan) was added to 140 g of water (DI-water) to prepare a slurry for coating the welding layer.

[0163] In Example 2 and Example 3 compared with Example 1, except that the glass transition temperature of the polymer adhesive contained in the welding layer 177 is different, the diaphragms of Example 2 and Example 3 were manufactured under the same conditions for the rest, and the welding force and anti-blocking properties were evaluated by the same method as Example 1.

[0164] (4) Process of manufacturing a composite diaphragm by coating

[0165] After coating the heat-resistant layer coating slurry on the porous substrate layer 179 using a conventional bar coating device, it was dried. Specifically, a heat-resistant layer 178 with a total thickness of 4μm was formed by double-sided coating in such a way that 2μm was coated on one side of the porous substrate layer 179, and a diaphragm with a total thickness of 13μm and coated (laminated) with the heat-resistant layer 178 was manufactured. Then, the welding layer 177 was coated / dried on the surface of the heat-resistant layer 178 using a bar coating device, and double-sided coating was performed in such a way that about 0.2μm was coated on one side, and a diaphragm (composite diaphragm) with a total thickness of 13.4μm and coated with the welding layer 177 / heat-resistant layer 178 was manufactured.

[0166] The manufactured composite diaphragm was wound into a Roll form with a length of about 100 m (meters) using a 3-inch core.

[0167] (5) High-temperature pressure hot welding and welding force evaluation process

[0168] Prepare the composite diaphragm and the negative electrode (second electrode) with lateral and vertical sizes of 50 mm (millimeters) x 50 mm respectively. First, in order to evaluate the welding force between the composite diaphragms, only half of each of the two composite diaphragms was laminated and placed between polytetrafluoroethylene sheets and welded by a hot press. In addition, in order to evaluate the welding force between the diaphragm and the electrode, only half of a composite diaphragm and a negative electrode were laminated and placed between polytetrafluoroethylene sheets and welded by a hot press. The hot press was executed for 10 s (seconds) under the hot welding conditions: 90 °C (Celsius temperature) and a pressure of 20 kgf / cm².

[0169] Then, a universal testing machine (UTM) was used to evaluate the welding force. The diaphragm + diaphragm film (first inspection piece) or diaphragm + negative electrode film (second inspection piece) that were welded in half were hung on the universal testing machine, and then the maximum strength when the welded part was separated was measured, and gf / mm (measured maximum strength / welding length) was used as the unit of the measured welding force.

[0170] (6) Evaluation of anti-blocking properties

[0171] While unwinding the diaphragm in the wound-up state, it was confirmed whether there was an adhesion phenomenon where the diaphragms adhered to each other and were difficult to unwind.

[0172] The method for measuring the adhesion characteristics of the diaphragm is carried out in accordance with ASTM D 1893 or ASTM D 3354. ASTM D1893 or ASTM D 3354 is a method for evaluating the ease of separation when separating two layers of films (or diaphragms).

[0173] As an example, the hand test is a method of manually separating two layers of films. Although it cannot be expressed in units, the degree of adhesion is qualitatively classified into the following four categories.

[0174] (1) No Blocking - This is a state where there is no adhesiveness between the two layers of films, and they can be easily separated from each other.

[0175] (2) Very Slight Blocking - The two layers of films adhere slightly, but can be separated with a very small force.

[0176] (3) Slight Blocking - The two layers of films are stuck together and require a considerable amount of force to separate, but there is no damage to the surface during separation.

[0177] (4) Blocking - Although the two layers of films can be separated from each other when forcibly peeled, the surface of the film is damaged.

[0178] In the above four categories, it is judged that the anti-adhesion requirements are met in the cases of (1) and (2), and it is judged that the anti-adhesion requirements are not met in the cases of (3) and (4).

[0179] Comparative Example 1

[0180] (1) Selection of the diaphragm (porous substrate layer)

[0181] A separator for secondary batteries with a thickness of 13 μm composed of only a single layer of polyethylene was used as the polyolefin-based microporous membrane.

[0182] (2) High-temperature pressure welding and weld strength evaluation process

[0183] Comparative Example 1 is an example where the diaphragm is composed only of a porous substrate layer. However, in Comparative Example 1, the first inspection piece and the second inspection piece were also prepared in the same manner as in other embodiments and welded in the same method. And the weld strength of the first inspection piece and the second inspection piece was evaluated under the same conditions as in other embodiments.

[0184] The melt bonding force and anti-sticking properties of Comparative Example 1 were evaluated by the same method as in other examples.

[0185] Comparative Examples 2 to 4

[0186] (1) Selection of the porous substrate layer

[0187] A separator for secondary batteries with a thickness of 9 μm composed of a single layer of polyethylene was used as the polyolefin microporous membrane.

[0188] (2) Manufacturing process of laminating (or coating) the heat-resistant layer 178 on the porous substrate layer

[0189] After uniformly dispersing 3 g of an inorganic dispersant and 231 g of boehmite (average particle size 0.7 μm, KC Corporation) in 150 g of water (DI-water), 14 g of a polyacrylate copolymer polymer binder (Tg 155 °C, ZEON Corporation, Japan) was added to prepare a slurry for coating the heat-resistant layer.

[0190] (3) Preparation process of the solution for coating the melt bonding layer 177.

[0191] 18 g of a polyacrylate copolymer polymer (Tg 25 °C, ZEON Corporation, Japan) was added to 140 g of water (DI-water) to prepare a slurry for coating the melt bonding layer.

[0192] (4) Process of manufacturing the composite separator by coating

[0193] Using a conventional coating device, the heat-resistant layer coating slurry was coated on the porous substrate layer 179 and dried to form a heat-resistant layer 178 with a thickness of 4 μm in total by double-sided coating in such a way that 2 μm was coated on each side of the porous substrate layer 179, thereby manufacturing a separator with a total thickness of 13 μm and having the heat-resistant layer 178 coated (laminated). Then, a rod coating device was used to coat / dry the melt bonding layer 177 on the surface of the heat-resistant layer 178, and double-sided coating was performed in such a way that about 0.2 μm was coated on each side, thereby manufacturing a separator (composite separator) with a total thickness of 13.4 μm and having the melt bonding layer 177 / heat-resistant layer 178 coated.

[0194] The manufactured composite separator was wound into a Roll form with a length of about 100 m using a 3-inch core.

[0195] For Comparative Examples 2 to 4, except for the different glass transition temperatures of the melt bonding layer 177, the melt bonding force and anti-sticking properties were evaluated by the same method as in other examples.

[0196] (5) High-temperature pressure hot melt bonding and melt bonding force evaluation process

[0197] Prepare the composite separator and the negative electrode (second electrode) with horizontal and vertical sizes of 50 mm (millimeters) x 50 mm respectively. First, in order to evaluate the bonding strength between the composite separators, stack only half of each of the two composite separators and place them between Teflon sheets, and then perform welding using a hot press. In addition, in order to evaluate the bonding strength between the separator and the electrode, stack only half of one composite separator and one negative electrode and place them between Teflon sheets, and then perform welding using a hot press. The hot press performs welding under the conditions of 90 °C (Celsius temperature) and a pressure of 20 kgf / cm² for 10 s (seconds).

[0198] Then, use a universal testing machine (UTM) to evaluate the bonding strength. Hang the half-welded separator + separator film (first inspection piece) or separator + negative electrode film (second inspection piece) on the universal testing machine, and then measure the maximum strength when the welded part separates. Use gf / mm (measured maximum strength / welding length) as the unit of the measured bonding strength.

[0199] (6)Evaluate the anti-blocking property

[0200] While unwinding the wound separator, check whether there is an adhesion phenomenon where the separators stick to each other and are difficult to unwind.

[0201] The method for measuring the adhesion property of the separator is carried out in accordance with ASTM D 1893 or ASTM D 3354. ASTM D1893 or ASTM D 3354 is a method for evaluating the ease of separation of two layers of films (or separators).

[0202] As an example, the hand test is a method of manually separating two layers of films. Although it cannot be expressed in units, the adhesion degree is qualitatively classified into the following four categories.

[0203] (1)No blocking - It is a state where there is no adhesiveness between the two layers of films, and they can be easily separated from each other.

[0204] (2)Very slight blocking - The two layers of films are slightly adhered, but can be separated with a very small force.

[0205] (3)Slight blocking - The two layers of films are stuck together and require a considerable amount of force to separate, but there is no damage to the surface during separation.

[0206] (4) There is blocking - Although they are separated from each other when the two layers of film are forcibly peeled off, the surface of the film is damaged.

[0207] In the above four categories, it is judged that the anti-blocking requirement is met in the cases of (1) and (2), and it is judged that the anti-blocking requirement is not met in the cases of (3) and (4).

[0208] Experimental Results

[0209] Table 1 and Table 2 below summarize and show the experimental results. Specifically, Table 1 shows Examples 1 to 3 and Comparative Examples 1 and 2, and Table 2 shows Examples 1 to 3 and Comparative Examples 4 and 5.

[0210] [Table 1]

[0211]

[0212] [Table 2]

[0213]

[0214] Comparative Example 1 directly used a polyethylene (PE) material separator formed only by a porous substrate layer without including a welding layer 177 / heat-resistant layer 178. Referring to Table 1 above, it can be confirmed that after welding by a hot press, neither the first inspection piece (separator / separator) nor the second inspection piece (separator / negative electrode) was welded.

[0215] Generally, in order to perform heat-sealing for attaching by melting a PE material film with heat, it is necessary to raise the temperature to near the melting point of PE so that they melt and adhere to each other. For the PE material used as a separator for secondary batteries, the thickness is very thin and it includes a large number of pores, so it is relatively more fragile than a general PE film. Therefore, in the case of using heat-sealing, it may be melted and broken or damaged.

[0216] Comparative Example 2 used a separator including a welding layer 177 using polymer particles with a low glass transition temperature (Tg). It can be seen from Table 1 that, compared with any of the examples in Table 1 other than Example 2, the welding force of the first inspection piece (separator / separator) of Comparative Example 2 is relatively slightly higher. In addition, it can be seen that in terms of the welding force of the second inspection piece (separator / negative electrode), Comparative Example 2 is relatively slightly higher than Examples 1, 2, and 3. However, it shows insufficient anti-blocking characteristics to prevent the blocking phenomenon of mutual adhesion between separators in the wound roll form of the separator. As a result, unnecessary adhesion occurs between the separators when stored in a roll form, so the conditions of Comparative Example 2 cannot be adopted in the actual manufacturing process.

[0217] Referring to Table 2, Comparative Example 3 is an example using a polymer adhesive with a glass transition temperature higher than that of Comparative Example 2 but lower than 30°C, and Comparative Example 4 is the result of an experiment conducted at 120°C, which is higher than that of Comparative Example 3. Comparative Example 3 failed to meet the anti-sticking property, and Comparative Example 4 failed to meet the bonding strength.

[0218] Therefore, referring to Table 1 and Table 2, the glass transition temperature (Tg) of the polymer particles (or polymer adhesive) contained in the welding layer 177 can exceed 30°C and be less than 90°C.

[0219] Preferably, referring to Examples 1 to 3, the glass transition temperature (Tg) of the polymer particles (or polymer adhesive) contained in the welding layer 177 can be 35°C (Celsius temperature) or higher and below 87°C.

[0220] On the other hand, there are various methods for bonding the separator to the electrodes (including the first electrode and the second electrode). A relatively more advantageous method can be adopted according to productivity and the achievement of secondary battery performance. Among them, the first method is a method of placing the electrodes on the separator, applying heat and pressure for bonding, and then winding the separator with the attached electrodes into a roll (Roll) form to manufacture a battery. The second method is a method of winding the electrodes and the separator into a jelly roll, applying heat and pressure to bond the electrodes and the separator, and then injecting electrolyte into the integrated jelly roll placed in the housing 113 and sealing it to manufacture a secondary battery (or battery cell). The third method is a method of injecting electrolyte after placing the jelly roll in the housing 113, and then applying heat and pressure to bond the electrodes and the separator.

[0221] The first and second methods apply heat and pressure to bond the electrodes and the separator in a state without electrolyte, so they can be called dry bonding methods. The third method bonds the electrodes and the separator in a state containing electrolyte, so it can be called a wet bonding method.

[0222] Depending on the type of polymer particles contained in the welding layer 177, the bonding strength may vary in the presence and absence of electrolyte. That is, the bonding strength may vary depending on the presence or absence of electrolyte and the composition materials of the positive and negative electrodes, so the type of polymer particles can be changed according to the design.

[0223] On the other hand, referring to Figure 2 and Figure 3 or Figure 4 and Figure 5 , the manufacturing method of the electrode assembly 10 according to the present disclosure can be described as follows.

[0224] That is, the manufacturing method of the electrode assembly 10 according to the present disclosure may include the steps of alternately arranging a first electrode 11 and a second electrode 15 having an electrode polarity different from that of the first electrode 11 between the diaphragms 17 along a preset stacking direction, and heating and bonding second parts 172 of the diaphragms 17 that are other parts of the diaphragms 17 and are located on both sides of a first part 171 that is part of the diaphragm 17, where the first part 171 overlaps with the first electrode 11 and the second electrode 15 along the stacking direction.

[0225] In the step of alternately arranging the first electrode 11 and the second electrode 15, the manufacturing method of the electrode assembly 10 according to the present disclosure may alternately arrange the first electrode 11 and the second electrode 15 between a plurality of diaphragms 17 stacked along the stacking direction or within spaces formed by folding a single diaphragm 17 into a zigzag shape between the single diaphragm 17.

[0226] After that, the manufacturing method of the electrode assembly 10 according to the present disclosure may perform the step of heating and bonding the second parts 172. In the step of heating and bonding the second parts 172, the manufacturing method of the electrode assembly 10 according to the present disclosure may bond the second parts 172 to each other by heat welding.

[0227] That is, the welding layer 177 including polymer particles with a glass transition temperature of 30 °C (Celsius temperature) or higher and 90 °C or lower and laminated on the second parts 172 may be heated at the glass transition temperature so that the second parts 172 are bonded to each other as described above. This can be referred to as heat welding. Generally, heat welding refers to bonding different components together by applying pressure and heat.

[0228] On the other hand, before welding the second parts 172, the first electrode 11 and / or the second electrode 15 may undesirably move between the diaphragms 17, so there is a risk that the arrangement of the first electrode 11 and the second electrode 15 is misaligned. Therefore, a jig or a pressure heating device 20 that can pressurize and heat the diaphragm 17 while restricting the movement of the electrode assembly 10 in the unbonded state may be required (see Figure 8 )

[0229] Figure 8 is an example of a jig or a pressure heating device for manufacturing an electrode assembly according to the present disclosure.

[0230] See Figure 8 , in the electrode assembly 10, the diaphragm 17 (see Figure 2 ) may be arranged along the stacking direction on the first electrode 11 (see Figure 2)and the second electrode 15 (see Figure 2 ) Therebetween. The separator 17 may be integrally formed and folded into a zigzag shape. Alternatively, a plurality of the separators 17 may be arranged between the first electrode 11 and the second electrode 15 in the stacking direction.

[0231] After that, the second portions 172 (see Figure 6 ) may be joined to each other to form the electrode assembly 10. The second portion 172 is a portion (remaining portion M) of the separator 17 that does not overlap with the first electrode 11 and the second electrode 15 in the stacking direction or a portion located on both sides of the first electrode 11 and the second electrode 15.

[0232] The second portions 172 may be joined by heat welding (or bonding). Alternatively, the second portions 172 may also be joined by methods such as vibration welding or ultrasonic welding.

[0233] To heat-weld the second portions 172, the electrode assembly 10 according to the present disclosure may use a pressure heating device 20. The pressure heating device 20 may include a jig for pressurizing and heating a region corresponding to the second portions 172 in the electrode assembly 10.

[0234] For this purpose, the pressure heating device 20 may include a first jig 21 and a second jig 22 arranged to be movable in the stacking direction to pressurize and heat the stacked portions of the second portions 172. The first jig 21 and the second jig 22 may be designed in a U shape to prevent pressure from being applied to the stacked portions of the first portion 171 (see Figure 6 ).

[0235] For pressurization, the first jig 21 and the second jig 22 should be able to move in the stacking direction. Therefore, the pressure heating device 20 may further include a driving portion (not shown in the figure) for moving the first jig 21 and the second jig 22. In addition, the first jig 21 and the second jig 22 may include heaters for heating the second portions 172.

[0236] In addition, the pressure heating device 20 may further include side jigs 23, 24 for supporting both sides of the electrode assembly 10 to prevent misalignment of the arrangements of the first electrode 11, the second electrode 15, and the separator 17 during the pressurization and heating of the first jig 21 and the second jig 22. The side jigs 23, 24 also come into contact with the second portions 172 respectively, and thus may include heaters for heating the second portions 172.

[0237] The present disclosure can be implemented in various forms, and its scope of rights is not limited to the above embodiments. Therefore, if a modified embodiment includes the constituent elements of the scope of the claims of the present disclosure, it should be regarded as falling within the scope of rights of the present disclosure.

Claims

1. A separator for a secondary battery, comprising: A porous substrate layer; And A welding layer laminated on at least one area of one or both sides of the porous substrate layer with a preset welding thickness, containing polymer particles with a glass transition temperature of 30 °C or more and 90 °C or less.

2. The separator for a secondary battery according to claim 1, wherein: The size of the polymer particles is 0.1 μm or more and 0.7 μm or less.

3. The separator for a secondary battery according to claim 1 or 2, wherein: The polymer particles are any one of acrylate and copolymers of acrylate or a combination thereof.

4. The separator for a secondary battery according to claim 1, wherein: The welding thickness is 1 μm or less.

5. The separator for a secondary battery according to claim 1 or 4, wherein: The shape of the polymer particles is amorphous.

6. The separator for a secondary battery according to claim 1, wherein Further comprising: A heat-resistant layer laminated on at least another area of one or both sides of the porous substrate layer with a preset heat-resistant thickness.

7. The separator for a secondary battery according to claim 6, wherein: The heat-resistant layer is laminated between the welding layer and the porous substrate layer in the area where the heat-resistant layer overlaps with the welding layer.

8. The separator for a secondary battery according to claim 6, wherein: Relative to 100% by weight of the entire composition, the heat-resistant layer contains 60 to 99% by weight of inorganic particles and 40 to 1% by weight of a polymer binder.

9. The separator for a secondary battery according to claim 8, wherein: The size of the inorganic particles is 0.1 μm or more and 2.0 μm or less.

10. An electrode assembly, comprising: A first electrode; A second electrode alternately laminated with the first electrode along a preset lamination direction and having an electrode polarity different from that of the first electrode; And A separator located between the first electrode and the second electrode and on the outermost sides of the first electrode and the second electrode along the lamination direction, including a first part overlapping with the first electrode or the second electrode along the lamination direction and second parts formed on both sides of the first part; The second part includes a welding layer, and the welding layer includes polymer particles with a glass transition temperature of 30 °C or more and 90 °C or less; At least a part of the second part is joined to each other by heating the welding layer.

11. The electrode assembly according to claim 10, wherein: The size of the polymer particles is 0.1 μm or more and 0.7 μm or less.

12. The electrode assembly according to claim 10 or 11, wherein: The polymer particles are any one of acrylate and copolymers of acrylate or a combination thereof.

13. The electrode assembly according to claim 10, wherein: The welding thickness as the lamination thickness of the welding layer is 1 μm or less.

14. The electrode assembly according to claim 10, wherein: There are a plurality of the first parts, and the plurality of the first parts are arranged at intervals.

15. The electrode assembly according to claim 10, wherein, The first part and the second part include: A porous substrate layer; and A heat-resistant layer laminated on one or both sides of the porous substrate layer with a preset heat-resistant thickness.

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