Electrode assembly and electrochemical device including the same

Abstract

The present invention relates to an electrode assembly and an electrochemical device including the same. The electrode assembly of the present invention includes unit electrodes and a strip-shaped separator, the separator being folded in a zigzag manner, and the unit electrodes are inserted into overlapping portions of the separator. The separator includes a porous substrate made of a polymer material and a porous coating layer including inorganic particles formed on each of an upper surface and a lower surface of the porous substrate. The thickness (Ts) of the porous substrate gradually decreases from the center to both ends in a length direction of the separator, and a total thickness (Tc) of the porous coating layer gradually increases toward both ends, and the total thickness (Ts+Tc) is maintained constant over the entire surface of the separator.

Description

Technical Field

[0001] The present invention relates to an electrode assembly and an electrochemical element including the same, specifically, a zigzag-stack type electrode assembly and a secondary battery including the same.

Background Art

[0002] Recently, the interest in energy storage technology has been increasing day by day. As the application fields are expanding to include mobile phones, video cameras, notebook computers, and even the energy of electric vehicles, the efforts in battery research and development are becoming more and more concrete. Electrochemical elements are the most prominent fields from such a perspective. In particular, recently, with the trend of miniaturization and weight reduction of electronic devices, the development of secondary batteries as small, lightweight, and high-capacity rechargeable batteries has become the focus of interest.

[0003] In addition, secondary batteries may be classified according to the structure of the electrode assembly having a positive electrode / separator / negative electrode structure. Typically, a jelly roll (winding type) electrode assembly having a structure in which a long sheet-type positive electrode and a negative electrode are wound with a separator interposed therebetween, and a stack type (laminated type) electrode assembly in which a large number of positive electrodes and negative electrodes cut out in units of a predetermined size are sequentially laminated with a separator interposed therebetween. However, such conventional electrode assemblies have several problems.

[0004] First, since the jelly roll electrode assembly is made by winding a long sheet-type positive electrode and a negative electrode in a dense state to form a cross-sectional cylindrical or elliptical structure, the stress induced by the expansion and contraction of the electrodes during charge and discharge is accumulated inside the electrode assembly. When such stress accumulation exceeds a certain limit, deformation of the electrode assembly occurs. The deformation of the electrode assembly causes the distance between the electrodes to become non-uniform, resulting in a rapid decrease in battery performance and threatening the safety of the battery due to internal short circuit. In addition, since the long sheet-type positive electrode and negative electrode must be wound, it is difficult to quickly wind while maintaining a constant distance between the positive electrode and the negative electrode, resulting in a problem of reduced productivity.

[0005] Second, since the stacked electrode assembly must sequentially stack a large number of positive electrode units and negative electrode units, a separate process for transferring the electrode plates for manufacturing the units is required, and a large amount of time and effort are required for the sequential stacking process, so there is a problem of low productivity.

[0006] FIG. 1 is a cross-sectional view schematically showing the structure of a stacked electrode assembly.

[0007] Referring to FIG. 1, as a stacked electrode assembly, an electrode assembly 1 of a Zig-Zag stacking (ZZS) method in which a positive electrode 5 and a negative electrode 7 are stacked in a zigzag manner with a separator 3 interposed therebetween has been developed.

[0008] After assembling the above-described electrode assembly of the zigzag stacking method, the battery is finally manufactured by fixing it through a hot press process. At this time, since the heat and pressure applied in the final hot press process are applied to the entire stacked electrode assembly, the amount of heat and pressure transmitted to the uppermost and lowermost portions in the stacking direction reference of the electrode assembly becomes large, resulting in large thickness deformation of the base materials of the uppermost and lowermost portions, which causes a problem of poor quality of the electrode assembly. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] Therefore, the problem to be solved by the present invention is to provide a separator capable of minimizing thickness deformation and pore damage of a porous structure during the manufacture of an electrode assembly of a zigzag stacking (ZZS) method, and a novel structure of an electrode assembly including the same.

[0010] Specifically, the present invention provides a novel structure of an electrode assembly that can minimize thickness deformation and pore damage of the porous structure despite the heat and pressure particularly greatly transmitted to the separation membrane regions at the uppermost and lowermost portions in the stacking direction of the electrode assembly touched by hot pressing in the hot pressing step for manufacturing the electrode assembly.

[0011] Accordingly, an object is to provide a separation membrane that maintains a high breakdown voltage and has improved insulation characteristics, and an electrode assembly including the same.

Means for Solving the Problems

[0012] In order to solve the above problems, According to one aspect of the present invention, a separation membrane for an electrochemical element of the following embodiment is provided.

[0013] According to the first embodiment, A strip-shaped separation membrane folded in a zigzag manner at predetermined intervals, the separation membrane includes a porous base material of a polymer material and porous coating layers formed on the upper and lower surfaces of the porous base material and containing inorganic particles, and the thickness Ts of the porous base material gradually decreases from the central portion to both side end portions based on the length direction of the separation membrane, and the total thickness Tc of the porous coating layer gradually increases toward both side end portions, and the total thickness Ts + Tc is maintained constant over the entire surface of the separation membrane. A separation membrane for an electrochemical element is provided.

[0014] According to the second embodiment, in the first embodiment, The thickness Ts of the porous base material is maintained constant from a predetermined position A in one end direction from the center line in the length direction of the separation membrane to a predetermined position A' in the opposite end direction, and the separation membrane is folded in a region AA' between the position A and the position A', and from the position A and the position A' to the end portions of the separation membrane respectively, the thickness Ts of the porous base material gradually decreases, and the total thickness Tc of the porous coating layer may increase toward both side end portions.

[0015] According to the third embodiment, in the second embodiment, The air permeability of the region AE from the position A to one-side end E or the region A'E' from the position A' to the other-side end E' may be 1 to 15 times the air permeability of the region AA' between the position A and the position A'.

[0016] According to the fourth embodiment, in the second embodiment or the third embodiment, The ratio Ts / Tc of the thickness Ts of the porous substrate to the overall thickness Tc of the porous coating layer at the position A may be 1 to 5.

[0017] According to the fifth embodiment, in any one of the first to fourth embodiments, The ratio Ts / Tc of the thickness Ts of the porous substrate to the overall thickness Tc of the porous coating layer over the entire surface of the separation membrane may be 0.5 to 5.

[0018] According to another aspect of the present invention, an electrode assembly of the following embodiment is provided.

[0019] According to the sixth embodiment, It includes a unit electrode and a strip-shaped separation membrane. The separation membrane is folded in a zigzag manner and the unit electrode is inserted into the portion where the separation membranes overlap. The separation membrane includes a porous substrate of a polymer material and porous coating layers formed on each of the upper and lower surfaces of the porous substrate and containing inorganic particles. The thickness Ts of the porous substrate gradually decreases from the central part to both-side end parts with reference to the length direction of the separation membrane, and the overall thickness Tc of the porous coating layer gradually increases toward both-side end parts. An electrode assembly is provided, characterized in that Ts+Tc is maintained constant over the entire surface of the separation membrane.

[0020] According to the seventh embodiment, in the sixth embodiment, The thickness Ts of the porous base material is maintained constant from a predetermined position A in one end direction to a predetermined position A' in the opposite end direction from the center line in the length direction of the separation membrane, and all or at least a part of the region AE from the position A to one end E and the region A'E' from the position A' to the other end E' are respectively arranged at the uppermost and lowermost stages in the stacking direction reference of the electrode assembly, and the thickness Ts of the porous base material gradually decreases toward the end portions of the separation membrane, and the overall thickness Tc of the porous coating layer may increase toward both end portions.

[0021] According to the eighth embodiment, in the sixth embodiment or the seventh embodiment, The region AA' from the position A to the position A' is not arranged at the uppermost and lowermost stages in the stacking direction reference of the electrode assembly, and the thickness Ts of the porous base material may decrease toward the end portions of the separation membrane in the regions arranged at the uppermost and lowermost stages in the stacking direction reference of the electrode assembly.

[0022] According to the ninth embodiment, in any one of the sixth embodiment to the eighth embodiment, The porous coating layers formed on the upper and lower surfaces of the porous base material are formed symmetrically with respect to each other with reference to the center line in the length direction of the separation membrane, and the thicknesses of the porous coating layers at the same arbitrary position orthogonal to the length direction of the separation membrane may be the same as each other, or the difference in thickness may be within 10%.

[0023] According to the tenth embodiment, in any one of the sixth embodiment to the ninth embodiment, The separation membrane is formed to have a symmetrical structure with reference to the center line in the length direction, and in the regions AE and A'E', the thicknesses Ts of the porous base materials formed at arbitrary positions separated by the same distance from the center line in the length direction of the separation membrane may be the same as each other, or the difference in thickness may be within 10%.

[0024] According to the eleventh embodiment, in any one of the sixth embodiment to the tenth embodiment, Over the entire surface of the separation membrane, the ratio Ts / Tc of the thickness Ts of the porous substrate to the total thickness Tc of the porous coating layer may be 0.5 to 5.

[0025] According to the 12th embodiment, in any one of the 6th to 11th embodiments, The ratio Ts / Tc of the thickness Ts of the porous substrate to the total thickness Tc of the porous coating layer at the position A may be 1 to 5.

[0026] According to the 13th embodiment, in any one of the 6th to 12th embodiments, After being fixed through a hot press process at a pressure of 3 MPa to 10 MPa at a temperature of 50°C to 110°C, the outermost thickness deformation rate of the electrode assembly may be 30% or less.

[0027] According to another aspect of the present invention, an electrochemical element of the following embodiment is provided.

[0028] According to the 14th embodiment, An electrochemical element is provided, characterized in that an electrode assembly according to any one of the 6th to 13th embodiments is housed in a case.

[0029] According to the 15th embodiment, in the 14th embodiment, The electrochemical element may be a lithium battery.

Advantages of the Invention

[0030] The electrode assembly according to an embodiment of the present invention can exhibit the characteristic that the thickness deformation of the separation membrane and the pore damage of the porous structure in the separation membrane are minimized despite the heat and pressure applied to the uppermost and lowermost portions in the stacking direction when fixed through a hot press process.

[0031] Thereby, it can be shown that there is an advantage of being able to provide an electrode assembly having excellent insulation characteristics.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0033] Hereinafter, the present invention will be described in detail.

[0034] In this specification, when a certain part "includes" a certain component, this means that, unless otherwise stated to the contrary, it does not exclude other components, but can further include other components.

[0035] As used herein, terms such as "about" and "substantially" are used in a sense that is from or close to the numerical value when manufacturing and material licensing errors inherent in the recited meaning are presented, and are used to prevent unscrupulous infringers from improperly using the disclosed content where an exact or absolute numerical value is recited for the understanding of the present application.

[0036] As used herein, the description of the term "A and / or B" means "A or B, or both of them".

[0037] The specific terms used in the following detailed description of the invention are for convenience and are not intended to limit the invention. Also, words indicating directions such as up, down, left, right, front, back, inside, outside, etc. indicate the directions in the drawings to which reference is made, or the directions towards or away from the geometric centers of the respective specified devices, systems and their components.

[0038] The present invention relates to a separation membrane for an electrochemical element and an electrode assembly including the same. Examples of the electrochemical element include a primary battery, a secondary battery, a supercapacitor, an electric double layer capacitor, etc. More specifically, the secondary battery can be a lithium ion secondary battery.

[0039] In one embodiment of the present invention, the electrode assembly includes a unit electrode and a strip-shaped separation membrane, and the separation membrane has a ZZZ-type electrode assembly structure in which the separation membrane is folded in a zigzag manner and the unit electrode is inserted into a portion where the separation membranes overlap.

[0040] Hereinafter, with reference to the drawings, the separation membrane, the electrode assembly including the separation membrane, and each component included in the electrode assembly will be described in more detail.

[0041] The separation membrane includes a porous substrate made of a polymer material and porous coating layers formed on the upper and lower surfaces of the porous substrate, respectively, and containing inorganic particles. Based on the length direction of the separation membrane, from the central part to both side end parts, the thickness Ts of the porous substrate gradually decreases, and the overall thickness Tc of the porous coating gradually increases toward both side end parts. Over the entire surface of the separation membrane, the overall thickness Ts + Tc is maintained constant.

[0042] In this specification, the "length direction" of the separation membrane indicates the direction in which two or more unit electrodes are arranged on the strip-shaped separation membrane.

[0043] In this specification, the "lamination direction" of the electrode assembly indicates the height direction in which unit cells are laminated when, during the assembly of the electrode assembly, unit electrodes are inserted into the portions where the separation membranes are laminated by being folded in a zigzag manner.

[0044] In this specification, the term "the thickness is maintained constant within a specific region" means that when measuring the thickness at any position within a specific region according to the same method, the measured thickness value exists within an error range of 5% or less. Specifically, when the deviation between the thickness values at any two positions within a specific region is within 5%, within 4%, within 3%, within 2%, within 1%, or 0% (i.e., there is no difference), it can be expressed that the thickness is maintained constant.

[0045] In this specification, the term "the thickness gradually increases within a specific region" means that when measuring the thickness in the same way according to a certain direction within a specific region, the thickness value continuously increases or increases discontinuously. The ratio at which the thickness value increases may be maintained constant within an error range of 5% or less, or may change discontinuously. However, the fact that the thickness gradually increases within the specific region preferably has a certain ratio and indicates that the thickness value continuously increases.

[0046] In this specification, the term "the thickness gradually decreases within a specific region" means that when the thickness is measured by the same method according to a certain direction within a specific region, the value of the thickness continuously decreases or discontinuously decreases. The ratio at which the value of the thickness decreases may be maintained constant within an error range of within 5%, or may change discontinuously. The fact that the thickness decreases within the specific region preferably has a certain ratio and can indicate that the value of the thickness continuously decreases.

[0047] In this specification, unless otherwise defined, the "thickness" of each component can indicate a value measured according to a known method capable of measuring the thickness of the separator membrane of the battery.

[0048] According to one embodiment, the thickness of the separator membrane and / or the porous substrate can indicate a value measured using a known thickness measuring instrument. For example, the thickness measuring instrument can use the VL-50S product of Mitutoyo Corporation, but is not limited thereto.

[0049] According to another embodiment, the thickness of the separator membrane and / or the porous substrate may be measured from the SEM image of the cross-section of the separator membrane and / or the porous substrate.

[0050] In one embodiment of the present invention, the thickness of the porous substrate may be measured in such a manner that after removing the porous coating layer from the separator membrane. For example, the porous coating layer can be removed using a solvent capable of dissolving the porous coating layer contained in the separator membrane, or after peeling off the porous coating layer using a tape, the thickness of the remaining porous substrate can be measured.

[0051] In one embodiment of the present invention, the thickness of the porous coating layer may be measured by the difference value of the thickness of the porous substrate measured as described above after measuring the thickness of the separator membrane, but the measuring method is not limited thereto.

[0052] In one embodiment of the present invention, the strip-shaped separation membrane is a long strip-shaped separation membrane having a predetermined width, and specifically, it can be a rectangular separation membrane having an aspect ratio of 1 or more. More specifically, the separation membrane may have a length of about 1,000 mm or more.

[0053] FIG. 2 is a diagram schematically showing the upper surface of the strip-shaped separation membrane according to one embodiment of the present invention. Referring to FIG. 2, the separation membrane 10 can be partitioned into an uppermost region (X), a lowermost region (Y), which are located at the uppermost or lowermost stage in the stacking direction when folded in the ZZS method during the manufacture of the electrode assembly, and an inner region Z located between the uppermost region and the lowermost region.

[0054] FIG. 3 is a diagram schematically showing the side surface of the strip-shaped separation membrane according to one embodiment of the present invention. Referring to FIG. 3, the separation membrane 10 includes a porous base material 11 and porous coating layers 12 formed on each of the upper and lower surfaces of the porous base material. In this specification, for convenience of explanation, the thickness of the porous base material is represented by Ts, and the total thickness of the porous coating layer is represented by Tc. At this time, the total thickness Tc of the porous coating layer is the thickness Tc of the porous coating layer formed on one surface of the porous base material 1 and the thickness Tc of the porous coating layer formed on the other surface. 2 It is to be shown as the sum of them.

[0055] Referring to FIG. 3, in the separation membrane 10, the thickness Ts of the porous base material gradually decreases from the central portion 10a toward both side end portions with respect to the length direction, the total thickness Tc of the porous coating layer gradually increases toward both side end portions, and the total thickness Ts + Tc is maintained constant over the entire surface of the separation membrane.

[0056] FIG. 4 is a diagram schematically showing a side view of a strip-shaped separation membrane according to an embodiment of the present invention. Referring to FIG. 4, the separation membrane includes a region AA' in which the thickness Ts of the porous substrate is maintained constant from the center 10a in the length direction to a predetermined position 101 in the direction of one end 103 and a predetermined position 102 in the direction of the opposite end 104. Further, the separation membrane includes a region AE in which the thickness Ts of the porous substrate gradually decreases from the position 101 toward the one end 103, and a region A'E' in which the thickness Ts of the porous substrate gradually decreases from the position 102 toward the opposite end 104.

[0057] FIG. 5 is a diagram schematically showing the structure of an electrode assembly 30 before assembly in which unit electrodes 20a and 20b are arranged on a strip-shaped separation membrane 10 according to an embodiment of the present invention. Referring to this, a plurality of first unit electrodes are arranged side by side at a predetermined interval on one side surface of the separation membrane. The separation interval between each unit electrode is preferably wider than the width of the first unit electrode when considering that the separation membrane is folded and each folded surface must cover the entire surface of the unit electrode. On the other hand, a plurality of second unit electrodes may be arranged in the same shape on the other side surface of the separation membrane. At this time, the first unit electrode and the second unit electrode may be arranged alternately so as not to overlap at all when viewed from the side. When arranged alternately as described above, it is preferable to separate them by a predetermined interval so that a space sufficient for the separation membrane to be folded can be secured between the adjacent first electrode and the second electrode. When arranged as described above, an electrode assembly having a structure in which the first electrode and the second electrode are laminated with the separation membrane interposed therebetween is obtained when the separation membrane is folded. The first unit electrode and the second unit electrode have opposite polarities to each other. For example, the first unit electrode may be a positive electrode and the second unit electrode may be a negative electrode, or vice versa.

[0058] FIG. 6 is a diagram schematically showing a method for manufacturing an electrode assembly according to an embodiment of the present invention. Referring to FIG. 6, the separation membrane 10 is folded in a zigzag manner, and the unit electrodes 20a and 20b are inserted into the overlapping portions of the separation membranes, and the separation membrane and the unit electrodes are laminated. After the insertion of the unit electrodes, the laminated structure is pressed to manufacture a ZZS type electrode assembly. When pressure is applied to the electrode assembly 30, since the pressure applied to the uppermost region 40a and the lowermost region 40b is relatively large compared to the inner region, the form of the separation membrane in the uppermost region 40a and / or the lowermost region 40b may be deformed. Therefore, the present invention may introduce a new structure into the porous base material and the porous coating layer existing in the uppermost region X and / or the lowermost region Y.

[0059] According to one aspect of the present invention, the electrode assembly can maintain a constant overall thickness over the entire surface of the separation membrane, maintain the interval at which the unit electrodes are arranged over the entire surface of the electrode assembly, and maintain the folding interval during the assembly of the electrode assembly. At the same time, as going to both side end portions of the separation membrane, the thickness of the porous base material gradually decreases, and the thickness of the porous coating layer formed on each of the upper and lower surfaces of the porous base material gradually increases. Therefore, when heat and / or pressure are applied through the outermost end portion during the manufacture of the electrode assembly, the heat resistance and impact resistance of the uppermost and lowermost portions with respect to the lamination direction of the electrode assembly are improved, and the deformation of the thickness and porosity of the central portion and the outermost end portion with respect to the lamination direction of the electrode assembly can be minimized.

[0060] In one embodiment of the present invention, at least a part of the region AA' may be arranged within the X region and / or the Y region.

[0061] In another embodiment of the present invention, the separation membrane may be folded in the region AA' between the position A and the position A'.

[0062] FIG. 7 is a diagram schematically showing a side structure when the separation membrane according to an embodiment of the present invention is folded in a zigzag manner. Referring to FIG. 7, a predetermined position 101 where the thickness of the porous base material starts to decrease toward the end portion is arranged within the uppermost region X, separated by a predetermined interval from the center in the length direction of the separation membrane 10. When a predetermined position 102 where the thickness of the porous base material starts to decrease toward the opposite end portion is arranged within the lowermost region Y, a part of the region AA' may be arranged in the uppermost region X and the lowermost region Y.

[0063] In another embodiment of the present invention, the region AA' is not arranged in the uppermost region X and the lowermost region Y with respect to the stacking direction reference of the electrode assembly, and it is preferable that all or at least a part of the region AE and the region A'E' are arranged in the X region and the Y region.

[0064] Specifically, since the Z region is a region that is relatively less affected by heat and / or pressure compared to the X region and the Y region when heat and / or pressure is applied during the manufacture of the electrode assembly, the region AA' is preferably the same as the Z region or arranged within the Z region. That is, the X region may be included within the AE region, and the Y region may be included within the A'E' region.

[0065] FIG. 8 is a diagram schematically showing a side structure when the separation membrane according to another embodiment of the present invention is folded in a zigzag manner. Referring to FIG. 8, the position A is a predetermined position 101 where the thickness of the porous base material starts to decrease toward the end portion of the separation membrane, and is located at the inner end of the uppermost region X with respect to the stacking direction reference of the electrode assembly. The position A' is a predetermined position 102 where the thickness of the porous base material starts to decrease toward the opposite end portion, and is located at the inner end of the lowermost region Y with respect to the stacking direction reference of the electrode assembly. It is possible that all of the region AE coincides with the X region, and all of the region A'E' coincides with the Y region. The separation membrane may be folded one or more times in the region AA'.

[0066] FIG. 9 is a diagram schematically showing a side structure when folding the separation membrane according to another embodiment of the present invention in a zigzag manner. Referring to FIG. 9, the position A is a predetermined position 101 where the thickness of the porous base material begins to decrease toward the end of the separation membrane, and is disposed inside at a predetermined distance from the uppermost region X in the stacking direction of the electrode assembly. The position A' is a predetermined position 102 where the thickness of the porous base material begins to decrease toward the opposite end, and is provided inside at a predetermined distance from the lowermost region Y in the stacking direction of the electrode assembly. A part of each of the regions AE and A'E' may include the regions X and Y, respectively.

[0067] In one embodiment of the present invention, the region AA' may be included, for example, at a length of 10% to 90%, 15% to 80%, 20% to 60%, or 20% to 50% based on the total length of the separation membrane. Accordingly, the regions AE and A'E' may be included at the end of the separation membrane such that the length obtained by subtracting the region AA' from the total length is the total length of the regions AE and A'E'.

[0068] In one embodiment of the present invention, the lengths of the regions AE and A'E' may be the same. That is, the lengths of the regions AE and A'E' may be included only by the length obtained by equally dividing the length obtained by subtracting the region AA' from the total length of the separation membrane.

[0069] In one embodiment of the present invention, the lengths of the regions AE and A'E' may be different from each other. At this time, it is preferable to assemble such that the region having a longer length is located at the lowermost part in the stacking direction of the electrode assembly from the viewpoint of minimizing the form deformation during the hot press process.

[0070] In one embodiment of the present invention, in the regions AE and A'E', the thickness Ts of the porous substrate decreases toward the end of the separation membrane, and the total thickness Tc of the porous coating layer increases, so that during the hot pressing process in the electrode assembly, morphological deformation can be prevented or reduced by high temperature and high pressure. However, the effects of the present invention are not limited thereto.

[0071] In one embodiment of the present invention, the air permeability of the separation membrane measured in the region AE or the air permeability of the separation membrane measured in the region A'E' can be 1 to 15 times the air permeability of the separation membrane measured in the region AA'. The separation membrane satisfying any embodiment of the present invention can exhibit a ratio of air permeability satisfying the above range. Specifically, the air permeability measured in the region AE or the region A'E' can be 2 to 14 times, 3 to 13 times, 4 to 12 times, 5 to 11 times, 6 to 10 times, or 7 to 9 times the air permeability measured in the region AA'. Preferably, it is 1 to 5 times.

[0072] In one embodiment of the present invention, the porous coating layers formed on the upper and lower surfaces of the porous substrate can be formed symmetrically with respect to each other based on the central portion in the length direction of the separation membrane.

[0073] Referring to FIGS. 3 and 4, when the porous coating layer formed on the upper surface of the porous substrate is named the first porous coating layer and the porous coating layer formed on the lower surface of the porous substrate is named the second porous coating, the first porous coating layer and the second porous coating layer can be formed in a shape that is line-symmetric with respect to the center line 10b in the thickness direction of the porous substrate.

[0074] Specifically, the porous coating layers formed on the upper and lower surfaces of the porous substrate are formed symmetrically with respect to each other based on the center line in the thickness direction of the separation membrane, and the thicknesses of the respective porous substrates at the same arbitrary position orthogonal to the length direction of the separation membrane are the same as each other or the difference in thickness can be within 10%.

[0075] For example, the thickness Tc of the first porous coating layer located on an imaginary line perpendicular to the length direction of the separation membrane at any position of the porous substrate 1 and the thickness Tc of the second porous coating layer 2 may be the same as each other, or if they are different from each other, the difference in their thicknesses may be within 10%.

[0076] More specifically, the thicknesses of the first porous coating layer and the second porous coating layer may have a difference within 10%, within 8%, within 5%, within 4%, within 3%, within 2%, within 1% or 0% (i.e., the same) from each other.

[0077] In one embodiment of the present invention, the separation membrane may be formed to have a symmetric structure with respect to the center 10a in the length direction.

[0078] In one embodiment of the present invention, the separation membrane can be formed to have a symmetric structure with respect to the center line 10a in the length direction and the center line 10b in the thickness direction. Referring to FIG. 4, the region AE from the predetermined position 101 to the end 103 and the region A'E' from the predetermined position 102 on the opposite side to the end 104 on the opposite side can be formed in a symmetric structure with respect to the center line 10a in the length direction and the center line 10b in the thickness direction.

[0079] Specifically, in the region AE and the region A'E', the respective thicknesses Ts of the porous substrates formed at arbitrary positions separated by the same distance from the center line 10a in the length direction of the separation membrane may be the same as each other, or the difference in thickness may be within 10%.

[0080] More specifically, in the region AE and the region A'E', the respective thicknesses Ts of the porous substrates formed at arbitrary positions separated by the same distance from the center line 10a in the length direction of the separation membrane may have a difference within 10%, within 8%, within 5%, within 4%, within 3%, within 2%, within 1% or 0% (that is, the same) from each other.

[0081] In one embodiment of the present invention, across the entire surface of the separation membrane, the ratio Ts / Tc of the thickness Ts of the porous substrate to the total thickness Tc of the porous coating layer can be 0.5 to 5. Specifically, the ratio (Ts / Tc) can be 0.8 to 3, 1 to 2, or 1 to 1.8. In the electrode assembly, as going towards the end portion with respect to the length direction of the separation membrane, the thickness Ts of the porous substrate gradually decreases, and the total thickness Tc of the porous coating layer gradually increases. Therefore, as going towards the end portion with respect to the length direction of the separation membrane, the ratio Ts / Tc can show a decreasing aspect.

[0082] In another embodiment of the present invention, the ratio Ts / Tc of the thickness Ts of the porous substrate to the total thickness Tc of the porous coating layer at the position A can be 1 to 5. Specifically, the ratio Ts / Tc at the position A can be 1 to 3, 1 to 2, or 1.5 to 1.8. In the electrode assembly, in the region AA' from the position A to the position A' as described above, it is a region where the thickness Ts of the porous substrate is maintained constant, and the Ts / Tc at the position A can show the maximum value of the ratio Ts / Tc across the entire surface of the separation membrane.

[0083] In one embodiment of the present invention, the porous substrate means a substrate in which a plurality of pores are formed inside by a porous ion-conduction barrier that allows ions to pass through while blocking electrical contact between the negative electrode and the positive electrode. The pores are formed in a structure connected to each other, and gas or liquid can pass from one surface of the substrate to the other surface. As such a porous substrate, from the viewpoint of providing a shut down function, a porous polymer film containing a thermoplastic resin can be used. Here, the shut down function means a function of preventing thermal runaway of the battery by blocking the movement of ions by dissolving the thermoplastic resin and closing the pores of the porous substrate when the temperature of the battery becomes high. As the thermoplastic resin, a thermoplastic resin with a melting point of less than 200°C is appropriate, and polyolefin is particularly preferable.

[0084] In one embodiment of the present invention, the porosity of the porous substrate can be, for example, 30% to 90%, 35% to 80%, 40% to 70%, 40% to 60%, or 40% to 50%. The porosity of the porous substrate can indicate, for example, a value measured by the formula of [true density of the material contained in the porous substrate - density of the porous substrate / true density * 100 (%)].

[0085] In one embodiment of the present invention, the thickness of the porous substrate is not particularly limited as long as it satisfies the above-described ratio (Ts / Tc), and can be, for example, 5 to 300 μm.

[0086] In one embodiment of the present invention, the porous coating layer is formed on each of the upper and lower surfaces of the porous substrate and contains inorganic particles. The inorganic particles can be filled in a dense state in the porous coating layer and have a number of fine pores due to the interstitial volume formed between the inorganic particles.

[0087] In one embodiment of the present invention, the porous coating layer may further contain a binder resin, and the inorganic particles may be coated on all or at least a part of the surface by the binder resin. At this time, the inorganic particles are surface-bonded and / or point-bonded through the binder resin. The inorganic particles and the binder resin in the porous coating layer can be contained in a weight ratio of 95:5 to 50:50.

[0088] In one embodiment of the present invention, the inorganic particles can be used without particular limitation as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly limited as long as oxidation and / or reduction reactions do not occur within the operating voltage range of the applied electrochemical element (for example, 0 to 5 V based on Li / Li + ). Non-limiting examples of these inorganic particles include BaTiO 3 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La xZr 1-y Ti y O 3 (PLZT, 0 < x < 1, 0 < y < 1), Pb(Mg 1 / 3 Nb 2 / 3 )O 3 -PbTiO 3 (PMN-PT), hafnia (HfO 2 )、SrTiO 3 、SnO 2 、CeO 2 、MgO、NiO、CaO、ZnO、ZrO 2 、SiO 2 、Y 2 O 3 、Al 2 O 3 、SiC、and TiO 2 etc. can be mentioned, and one or more of these may be included.

[0089] In one embodiment of the present invention, when the porous coating layer contains a binder resin, the binder resin can include, for example, a polyvinylidene fluoride-based resin (PVdF-based resin). In one embodiment of the present invention, the PVdF-based resin can include one or more of a homopolymer of vinylidene fluoride (i.e., polyvinylidene fluoride), a copolymer with a monomer copolymerizable with vinylidene fluoride, and a mixture thereof. In one embodiment of the present invention, as the monomer, for example, a fluorinated monomer and / or a chlorine-based monomer can be used. Non-limiting examples of the fluorinated monomer include vinyl fluoride; trifluoroethylene (TrFE); chlorotrifluoroethylene (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), etc., and one or more of these may be included.

[0090] In one embodiment of the present invention, from the viewpoint of the adhesive strength during adhesion of the PVdF-based resin, those having a Tm of 140°C or lower can be used. For this purpose, the PVdF-based resin can include a copolymer of a vinylidene fluoride unit and another monomer copolymerizable with the vinylidene fluoride unit. Examples of such copolymers include PVDF-TrFE, PVDF-TFE, PVDF-CTFE, PVDF-HFP, etc., and one or more of these can be included.

[0091] On the other hand, as the binder resin, in addition to the PVdF-based resin, if necessary, a (meth)acrylic-based polymer resin can be further included. The (meth)acrylic-based polymer contains (meth)acrylic acid ester as a monomer, and non-limiting examples thereof include (meth)acrylic polymers containing butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, n-octyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, and tetradecyl (meth)acrylate as monomers.

[0092] In one embodiment of the present invention, the separation membrane can be manufactured by applying a slurry for forming an inorganic coating layer containing the inorganic particles or the binder resin and the inorganic particles onto a porous substrate, and drying the solvent and / or the binder resin to integrally form a porous coating layer on the porous substrate. The manufacturing method of the separation membrane can be applied without limitation as long as the porous coating layer is formed on each of the upper and lower surfaces of the porous substrate and a separation membrane having the above-described shape can be obtained, and it is not limited to a specific manufacturing method.

[0093] In one embodiment of the present invention, the thickness of the porous coating layer is not particularly limited as long as it satisfies the above-described ratio (Ts / Tc), and can be, for example, 3 to 50 μm.

[0094] The electrode assembly according to the present invention includes a separator having the above-described shape, and includes one or more pairs of unit electrodes spaced apart from each other on the separator.

[0095] In one embodiment of the present invention, the unit electrode is a normal positive electrode and / or negative electrode used in an electrochemical device, and the positive electrode and the negative electrode are each a current collector coated with an electrode active material, and their size and shape are not particularly limited.

[0096] When the electrode is a positive electrode, the positive electrode active material can be, for example, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide combining these, or a mixture of two or more of these, but is not limited thereto.

[0097] When the electrode is a negative electrode, the negative electrode active material can be, for example, lithium metal or a lithium alloy, soft carbon, hard carbon, natural graphite, kish graphite, pyrolytic carbon, meso-carbon microbeads, meso-carbon microbeads, mesophase pitches, petroleum or coal tarpitch derived cokes, or a mixture of two or more of these, but is not limited thereto.

[0098] The electrode assembly according to the present invention having the above structure shows an excellent effect of maintaining the form of the electrode assembly because the heat resistance and impact resistance of the electrode assembly are excellently improved even when pressure is applied in the stacking direction of the electrode assembly by a hot press process.

[0099] In one embodiment of the present invention, after being fixed by a hot press process at a pressure of 3 MPa to 10 MPa at a temperature of 50°C to 110°C, the thickness deformation rate of the outermost part of the electrode assembly can be 30% or less.

[0100] In another embodiment of the present invention, the hot press process may specifically be performed at a pressure of 3 MPa to 10 MPa at a temperature of 50°C to 110°C. At this time, after being fixed by the hot press process, the thickness deformation rate of the outermost part of the electrode assembly can be 30% or less.

[0101] In this specification, after being fixed by a normal method for fixing the electrode assembly, such as the hot press process, the thickness deformation rate of the outermost part of the electrode assembly can be shown by measuring the thickness of the electrode assembly before and after fixing and using the formula [(thickness before press - thickness after press) / thickness before press * 100(%)].

[0102] In another embodiment of the present invention, after being fixed by a normal method for fixing the electrode assembly, such as the hot press process, the thickness deformation rate of the outermost part of the electrode assembly can specifically be shown as 30% or less, 25% or less, 20% or less, 15% or less. More specifically, after being fixed by the hot press process, the thickness deformation rate of the outermost part of the electrode assembly can be 0% or more, 5% or more, or 10% or more, up to 15% or less, for example, 11% to 12%.

[0103] In one embodiment of the present invention, when showing the thickness deformation rate before and after fixing, the outermost part of the electrode assembly can indicate a region where the thickness Ts of the porous base material gradually decreases and the total thickness Tc of the porous coating layer gradually increases in the separation membrane.

[0104] In another embodiment of the present invention, when indicating the thickness deformation rate before and after fixation, the outermost part of the electrode assembly can indicate all or at least a part of the above-described regions AE and A'E'.

[0105] In another embodiment of the present invention, after being fixed by a normal method for fixing the electrode assembly, such as the hot process step, the thickness deformation rate of the innermost part of the electrode assembly can specifically be 15% or less.

[0106] In one embodiment of the present invention, when indicating the thickness deformation rate before and after fixation, the innermost part of the electrode assembly can indicate the region where the thickness Ts of the porous base material is kept constant in the separation membrane.

[0107] In another embodiment of the present invention, when indicating the thickness deformation rate before and after fixation, the innermost part of the electrode assembly can indicate all or at least a part of the above-described region AA'.

[0108] In the present invention, by including the separation membrane having the above-described form, the electrode assembly can show the effect that the withstand voltage characteristics of the battery are improved, the breakdown voltage becomes higher, and the short-circuit occurrence rate (Hi-pot failure rate) is reduced even under high voltage conditions.

[0109] The breakdown voltage means the maximum voltage that the insulator can withstand. Breakdown means that when a voltage is applied to the insulator, when the voltage reaches a certain value or more, the insulator is broken and loses its insulating performance.

[0110] The breakdown voltage can be measured, for example, with an AC / DC / IR Hi-Pot tester. For example, after hot pressing and bonding a mesh of stainless steel material and a porous substrate under the conditions of 90°C, 4 MPa, and 1 second, a DC current of 0.5 mA is set here, and the voltage is increased at 100 V / s (voltage 3 kV, ramp up time 3 s). When the experiment starts, the measurement is completed when a short circuit occurs while the voltage is rising, and the voltage at that time is defined as the breakdown voltage.

[0111] In addition, the evaluation of the short circuit occurrence rate (Hi-Pot failure rate) can be measured by a method of confirming the voltage shown by the test pieces in the lowest 1% showing a low breakdown voltage by Weibull distribution analysis among all the test pieces to be tested.

[0112] In one embodiment of the present invention, after being fixed by an ordinary method for fixing the electrode assembly such as the hot pressing process, the breakdown voltage of the porous substrate existing on the outermost part of the electrode assembly can show 800 kV / mm or more.

[0113] In another embodiment of the present invention, after being fixed by an ordinary method for fixing the electrode assembly such as the hot pressing process, the breakdown voltage of the porous substrate existing on the outermost part of the electrode assembly can specifically show a value of 1,000 kV / mm or more or 1,500 kV / mm or more.

[0114] In one embodiment of the present invention, the electrochemical element is one in which the above-described electrode assembly is housed in a case.

[0115] In one embodiment of the present invention, the case can adopt one that is usually used as a battery case, and there is no particular limitation on the outer shape depending on the use of the battery. For example, the case may be a cylindrical shape using a can, a rectangular shape, a pouch type, a coin type, or the like.

[0116] Once the electrode assembly as described above is completed, it can be housed in a case and sealed in a normal manner to manufacture an electrochemical element. At this time, the electrochemical element can be, for example, a lithium secondary battery.

[0117] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are for illustrative purposes only and the scope of the present invention is not limited thereto.

[0118] Example 1 [Manufacture of Separation Membrane] A separation membrane was manufactured according to the following method.

[0119] In each component, the porosity was measured according to the formula [(true density of the applied substance - density of the component) / true density * 100 (%)].

[0120] In each component, the thickness was measured using a thickness measuring instrument (VL-50S, manufactured by Mitutoyo Corporation).

[0121] [Manufacture of Porous Substrate] Three types of polyethylene polymers and polypropylene polymers with different molecular weights and an antioxidant were mixed in an appropriate ratio and a porous substrate for use in a separation membrane was manufactured according to a known method. The three types of polyethylene polymers used were PE40 (Mw 400,000 g / mol), PE90 (Mw 900,000 g / mol), and PE150 (Mw 1,500,000 g / mol), and the polypropylene polymer was PP35 (Mw 350,000 g / mol). The porosity of the manufactured porous substrate was 45%.

[0122] The porous substrate had an overall width of 350 mm and a length of 1 m, and the thickness measured at both ends was 12 μm each. It was manufactured such that the thickness gradually increased from both ends to the 0.3 m point in the length direction and then maintained a thickness of 15 μm from the 0.3 m point. [Manufacture of Porous Coating Layer]

[0123] An appropriate solvent was mixed with a PVDF-HFP binder (Mw 500,000 g / mol, 15 wt% HFP) and inorganic particles at a weight ratio of 80:20 to produce a slurry for inorganic coating.

[0124] The slurry for inorganic coating produced above was applied to the entire surface of the porous substrate by the dip coating method, dried according to the humid phase separation method, and a porous coating layer was formed on each of the upper and lower surfaces of the porous substrate produced above.

[0125] The porous coating layers formed on each of the upper and lower surfaces were each 6 μm thick when measured from both ends, and the thickness gradually decreased from both ends to the 0.3 m point in the length direction and then was maintained at a thickness of 4.5 μm from the 0.3 m point.

[0126] Thereby, a separation membrane with an overall thickness maintained at 24 μm was produced over the entire surface.

[0127] [Manufacture of Electrode Assembly] An electrode assembly was manufactured using the separation membrane produced above. Specifically, 17 positive electrodes and 16 negative electrodes were arranged crossing the upper and lower surfaces of the separation membrane. At this time, the point where the end of the positive electrode is located on one surface and the point where the end of the negative electrode is located on the other surface were spaced apart and cross-arranged so that the horizontal interval on the plane was 3 mm. Lithium cobalt oxide LCO was used as the positive electrode active material, and graphite was used as the negative electrode active material (N / P ratio > 100).

[0128] Comparative Example 1 [Manufacture of Separation Membrane] Manufacture of Porous Substrate A porous substrate was manufactured in the same manner as in Example 1, except that it was formed with a constant thickness of 15 μm without thickness change over the entire length direction.

[0129] Manufacture of Porous Coating Layer A porous coating layer was formed in the same manner as in Example 1, except that it was formed with a constant thickness of 4.5 μm throughout the length direction without any thickness change. Thus, a solid separator with a thickness of 24 μm was manufactured.

[0130] [Manufacture of Electrode Assembly] An electrode assembly was manufactured in the same manner as in Example 1, except that the separator manufactured above was used.

[0131] [Evaluation of Thickness Change Rate during Hot Pressing Process] The electrode assemblies of Example 1 and Comparative Example 1 manufactured above were each hot pressed and fixed under the pressure conditions of 90 °C and 6.5 MPa for 6 seconds. At this time, the thickness deformation rate in each region before and after hot pressing was measured, and the results are shown in Table 1 below.

[0132] The thickness of the separator after pressing was measured using a thickness measuring instrument (VL-50S, manufactured by Mitutoyo Corporation). The thickness of the porous substrate was measured using the same thickness measuring instrument after peeling the porous coating layer from the separator using tape. At this time, the thickness of the porous substrate was verified with the above measured values using the thickness value obtained from the SEM image of the separator cross-section before peeling the porous coating layer.

[0133] In Table 1 below, the innermost part indicates the region where the thickness of the porous substrate is maintained constant, and the outermost part indicates the region where the thickness of the porous substrate decreases towards both ends.

[0134]

Table 1

[0135] As confirmed from Table 1 above, although the innermost changes before and after hot pressing showed similar levels in Comparative Example 1 and Example 1, in each of the uppermost and lowermost parts of the electrode assembly in the stacking direction reference, the electrode assembly of Example 1 including a separator in which the thickness of the porous coating layer gradually increases while the thickness of the porous base material gradually decreases towards both ends showed a significantly reduced outermost deformation rate.

[0136] [Durability Evaluation of Electrode Assembly] In order to measure the thickness deformation rate as described above, the breakdown voltage was measured using the porous base materials of Example 1 and Comparative Example 1 from which the porous coating layer was removed by the taping process, and the results are shown in Table 2 below.

[0137] The breakdown voltage was measured using an AC / DC / IR Hi-Pot tester. Specifically, after adhering the porous base material to a stainless steel mesh material by hot pressing at 90 °C, 4 MPa for 1 second, a DC current was set to 0.5 mA and the voltage was set to increase by 100 V / s (Voltage 6 kV, ramp up time 6 s), and it was evaluated by measuring the voltage when a short circuit occurred.

[0138] The breakdown voltage shows the result measured for the outermost porous base material of the electrode assembly.

[0139]

Table 2

[0140] It is confirmed from Table 2 above that the breakdown voltage of Example 1 is far superior to that of Comparative Example 1, and it is presumed that this is because the pore damage rate of the porous base material is low even after the hot pressing process due to the special structure of the separator of Example 1.

[0141] As described above with reference to the embodiments and drawings of the present invention, those having ordinary knowledge in the field to which the present invention pertains can make various applications and modifications within the scope of the present invention based on the above content.

Description of Symbols

[0142] 1 Electrode assembly 3 Separation membrane 5 Positive electrode 7 Negative electrode 10 Separation membrane 11 Porous substrate 12 Porous coating layer 10a Center in the length direction of the separation membrane 10b Center in the thickness direction of the separation membrane 20a Negative electrode 20b Positive electrode 30 Electrode assembly 40 Pressing process of the electrode assembly 40a Uppermost region of the electrode assembly 40b Lowermost region of the electrode assembly 101 Position A 102 Position A' 103 Position E 104 Position E' X Reference uppermost region in the stacking direction Y Reference lowermost region in the stacking direction Z Reference inner region in the stacking direction Ts Thickness of the porous substrate Tc 1 , Tc 2 Thickness of the porous coating layer

Claims

1. A strip-shaped separation membrane that is folded in a zigzag manner at predetermined intervals, wherein the separation membrane includes a porous base material made of a polymer material and porous coating layers formed on each of the upper and lower surfaces of the porous base material and containing inorganic particles, the thickness (Ts) of the porous base material is maintained constant from a predetermined position (A) in one end direction from the center line in the length direction of the separation membrane to a predetermined position (A') in the opposite end direction, the separation membrane is folded in the region (AA') between the position (A) and the position (A'), from the position (A) and the position (A') respectively towards the end portions of the separation membrane, the thickness (Ts) of the porous base material gradually decreases, and the total thickness (Tc) of the porous coating layer increases towards both end portions, a separation membrane for an electrochemical element, wherein the total thickness (Ts + Tc) is maintained constant over the entire surface of the separation membrane.

2. The air permeability of the region (AE) from the position (A) to one end (E) or the region (A'E') from the position (A') to the other end (E') is 1 to 15 times the air permeability of the region (AA') between the position (A) and the position (A'). The separation membrane for an electrochemical element according to Claim 1.

3. The ratio (Ts / Tc) of the thickness (Ts) of the porous base material to the total thickness (Tc) of the porous coating layer at the position (A) is 1 to 5. The separation membrane for an electrochemical element according to Claim 1.

4. Over the entire surface of the separation membrane, the ratio (Ts / Tc) of the thickness (Ts) of the porous base material to the total thickness (Tc) of the porous coating layer is 0.5 to 5. The separation membrane for an electrochemical element according to Claim 1.

5. Including a unit electrode and a strip-shaped separation membrane, the separation membrane is folded in a zigzag manner and the unit electrode is inserted into the portion where the separation membranes overlap, the separation membrane includes a porous base material made of a polymer material and porous coating layers formed on each of the upper and lower surfaces of the porous base material and containing inorganic particles, the thickness (Ts) of the porous base material is maintained constant from a predetermined position (A) in one end direction from the center line in the length direction of the separation membrane to a predetermined position (A') in the opposite end direction, All or at least a part of the region (AE) from the position (A) to one-side end (E) and the region (A'E') from the position (A') to the other-side end (E') are respectively arranged at the uppermost and lowermost positions with respect to the stacking direction reference of the electrode assembly body, and the thickness (Ts) of the porous base material gradually decreases toward the end portions of the separation membrane, and the overall thickness (Tc) of the porous coating layer increases toward both-side end portions, An electrode assembly body in which the overall thickness (Ts + Tc) is maintained constant over the entire surface of the separation membrane.

6. The region (AA') from the position (A) to the position (A') is not arranged at the uppermost and lowermost positions with respect to the stacking direction reference of the electrode assembly body, The electrode assembly body according to claim 5, wherein in the regions of the separation membrane arranged at the uppermost and lowermost positions with respect to the stacking direction reference of the electrode assembly body, the thickness (Ts) of the porous base material decreases toward the end portions of the separation membrane.

7. The porous coating layers formed on the upper surface and the lower surface of the porous base material are formed symmetrically with respect to each other with reference to the center line in the length direction of the separation membrane, and the thicknesses of the porous coating layers at the same arbitrary position orthogonal to the length direction of the separation membrane are the same as each other or the difference in thickness is within 10%, The electrode assembly body according to claim 5.

8. The separation membrane is formed to have a symmetric structure with reference to the center line in the length direction, In the region (AE) and the region (A'E'), the thicknesses (Ts) of the porous base materials formed at arbitrary positions separated by the same distance from the center line in the length direction of the separation membrane are the same as each other or the difference in thickness is within 10%, The electrode assembly body according to claim 5.

9. The electrode assembly body according to claim 5, wherein the ratio (Ts / Tc) of the thickness (Ts) of the porous base material to the overall thickness (Tc) of the porous coating layer is 0.5 to 5 over the entire surface of the separation membrane.

10. The electrode assembly body according to claim 5, wherein the ratio (Ts / Tc) of the thickness (Ts) of the porous base material to the overall thickness (Tc) of the porous coating layer at the position (A) is 1 to 5.

11. After being fixed through a hot press process at a temperature of 50°C to 110°C and a pressure of 3 MPa to 10 MPa, the outermost thickness deformation rate of the electrode assembly is 30% or less. The electrode assembly according to any one of claims 5 to 10.

12. An electrochemical element in which the electrode assembly according to claim 5 is housed in a case.

13. The electrochemical element according to claim 12, wherein the electrochemical element is a lithium secondary battery.

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