Secondary battery unit cell including separator having insulating coating layer formed thereon, and method for manufacturing same

Abstract

The unit cell for a secondary battery according to the present embodiment includes an electrode plate having a tab formed thereon, and a separator, and the separator includes a first coating portion having an organic / inorganic composite porous coating layer formed on at least one surface of a base substrate, and a second coating portion having an insulating coating layer formed thereon.

Description

[Technical field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0002664 dated January 8, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a unit cell for a secondary battery including a separator having an insulating coating layer formed thereon, and a method for manufacturing the same. [Background technology]

[0003] The rapid increase in the use of fossil fuels has led to an increased demand for alternative and clean energy, and as part of this, the most actively researched field is the field of electrochemical power generation and storage.

[0004] At present, a representative example of an electrochemical element that uses such electrochemical energy is a secondary battery, and the range of its use is tending to expand day by day.

[0005] Recently, the demand for secondary batteries as energy sources has been increasing rapidly due to technological developments and increasing demand for portable devices such as portable computers, mobile phones, and cameras. Among such secondary batteries, much research has been conducted on lithium secondary batteries, which exhibit high charge / discharge characteristics and life characteristics and are environmentally friendly, and they have been commercialized and are widely used.

[0006] In general, a lithium secondary battery is manufactured by impregnating an electrode assembly, which includes a positive electrode, a negative electrode, and a porous separator, with a lithium non-aqueous electrolyte.

[0007] In order to prevent the active material from protruding from the electrodes, the positive and negative electrodes are coated with an electrode active material, and then an insulating treatment is performed by coating an insulating liquid on the electrode tabs or attaching an insulating tape thereto.

[0008] This insulation process prevents active material protrusion and reduces Li plating, which contributes to improving the safety of the cell.

[0009] In particular, in the case of an ESS (Energy Storage System) electrode, a positive electrode is produced by simultaneously coating an insulating coating solution with an active material slurry, and the positive electrode is laminated with a separator to form a unit cell for a secondary battery.

[0010] This is shown in Figures 1 and 2 below.

[0011] First, referring to FIG. 1, when the positive electrode slurry is coated, an insulating coating liquid is also coated on the tab portion to form a positive electrode 10 having an insulating coating layer 13 applied to the boundary portion between the active material layer 11 and the tab 12. The positive electrode 10 is then laminated with a separator 20 to manufacture a unit cell 30.

[0012] In addition, referring to FIG. 1 together with FIG. 2, the unit cell 30 including the positive electrode 10 having the insulating coating layer 13 formed on the tab 12 and the separator 20 manufactured in this manner may be stacked with the negative electrode 40 and an additional separator 50 to form a new unit cell 60.

[0013] However, when the electrode having such a structure is simultaneously coated with the electrode slurry and the insulating coating liquid, it is difficult to align the insulating coating liquid, and in this process, a large amount of electrode slurry is lost.

[0014] Furthermore, when forming a unit cell for a secondary battery, folding of the separator, which is a polymer substrate, often occurs when stacking electrodes and a separator, jeopardizing the safety of the secondary battery.

[0015] Therefore, there is a pressing need for technological development that can solve these problems and ensure the safety of secondary batteries by forming an insulating coating layer. Summary of the Invention [Problem to be solved by the invention]

[0016] An object of the present invention is to solve the above-mentioned problems of the prior art and the technical problems that have been required in the past.

[0017] Specifically, an object of the present invention is to provide a unit cell for a secondary battery and a manufacturing method thereof, which can improve the safety of the secondary battery by applying an insulating coating layer, while solving the problem of electrode loss caused by difficulty in aligning when applying an insulating coating solution, and can also prevent the problem of folding of a separator. [Means for solving the problem]

[0018] To achieve this object, a unit cell for a secondary battery according to an embodiment of the present invention comprises: The unit cell includes an electrode plate having a tab formed thereon and a separator, The separator includes a first coating portion having an organic / inorganic composite porous coating layer formed on at least one surface of a base substrate, and a second coating portion having an insulating coating layer formed on at least one surface of the base substrate.

[0019] In one specific example, the tab is formed on one side of the electrode plate, and the second coating portion is formed on one end of the separation membrane at a portion overlapping the tab based on the formation direction of the tab, and a first coating portion is formed parallel to the second coating portion in the remaining portion, and the electrode may be laminated on the separation membrane so that the tab is located in the second coating portion of the separation membrane.

[0020] In one specific example, the tab is formed on one or both sides of the electrode plate, and a second coating portion is formed on one end of the separation membrane at a portion overlapping with the tab based on the formation direction of the tab and the corresponding other end of the separation membrane, and a first coating portion is formed parallel to the second coating portion in the remaining portion, and the electrode may be laminated on the separation membrane so that the tab is located in the second coating portion at one end or both ends.

[0021] Alternatively, the electrode plate may be a positive electrode plate.

[0022] In this case, the secondary battery unit cell may further include a negative electrode plate, and the separator may be interposed between the positive electrode plate and the negative electrode plate.

[0023] In this case, the negative electrode plate may be larger than the positive electrode plate in four dimensions.

[0024] In addition, the secondary battery unit cell may further include an additional separator including a first coating portion and a second coating portion identical to the separator, and the additional separator may be laminated on the other side of the positive electrode plate or the negative electrode plate that does not face the separator.

[0025] In this case, the second coated portion of the separation membrane and the second coated portion of the additional separation membrane may be bonded to each other.

[0026] In one specific example, the insulating coating layer may be a polymer coating layer including a PVdF-based material.

[0027] Meanwhile, according to another embodiment of the present invention, there is provided an electrode assembly including the unit cell for a secondary battery, and a lithium secondary battery including the electrode assembly and a lithium salt non-aqueous electrolyte.

[0028] Furthermore, according to yet another embodiment of the present invention, there is provided a method for manufacturing a unit cell for a secondary battery, comprising the steps of: (a) providing an electrode plate having tabs formed thereon; (b) forming a first coating portion of an organic / inorganic composite porous coating layer and a second coating portion of an insulating coating layer on at least one surface of a base substrate to manufacture a separator; and (c) laminating the electrode and a separator; Including, The first coated portion and the second coated portion are formed by simultaneously coating the first coated portion and the second coated portion. [Brief description of the drawings]

[0029] [Figure 1] 1 is a schematic diagram showing a conventional process for manufacturing a unit cell for a secondary battery. [Diagram 2] FIG. 2 is a cross-sectional view of the unit cell of FIG. [Diagram 3] 2A and 2B are schematic views and cross-sectional views of a process for manufacturing a unit cell for a secondary battery according to an embodiment of the present invention; [Figure 4] 4A and 4B are schematic views and cross-sectional views of a process for manufacturing a unit cell for a secondary battery according to still another embodiment of the present invention. [Diagram 5] 4A and 4B are schematic views and cross-sectional views of a process for manufacturing a unit cell for a secondary battery according to still another embodiment of the present invention. [Figure 6] 4 is a cross-sectional view of a unit cell for a secondary battery according to still another embodiment of the present invention. [Figure 7] 4 is a cross-sectional view of a unit cell for a secondary battery according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The present invention will now be described in more detail to aid in understanding the present invention.

[0031] The terms and words used in this specification and the claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept that is appropriate to the technical idea of ​​the present invention, based on the principle that the inventor himself can appropriately define the concept of the term in order to explain the invention in the best possible way.

[0032] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless a different meaning is clearly indicated in the context.

[0033] In this specification, terms such as "comprise", "comprise", or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0034] According to one embodiment of the present invention, A unit cell for a secondary battery, The unit cell includes an electrode plate having a tab formed thereon and a separator, The separator is provided as a unit cell for a secondary battery including a first coating part having an organic / inorganic composite porous coating layer formed on at least one surface of a base substrate, and a second coating part having an insulating coating layer formed on at least one surface of the base substrate.

[0035] Here, the term "unit cell" refers to a part of an electrode assembly for manufacturing a secondary battery. That is, it can refer to a separate member for manufacturing an electrode assembly such as a stack-folding type or an L&S (lamination and stack) type, i.e., a unit cell such as a bi-cell or a full cell, but it can also refer to a part of the electrode assembly in all types of electrode assemblies. Therefore, when the entire electrode assembly has a configuration in which the first coating part of the organic / inorganic composite porous coating layer and the second coating part of the insulating coating layer are formed on at least one separator, the present invention is included in the scope of the present invention.

[0036] The positions at which the first and second coated portions are formed are not limited as long as the second coated portion is positioned at a position where the tab of the electrode plate is formed.

[0037] For example, the tab may be formed on one side of the electrode plate, and the second coating portion may be formed on one end of the separator at a portion overlapping with the tab based on the direction in which the tab is formed, and a first coating portion may be formed parallel to the second coating portion in the remaining portion, and the electrode may be stacked on the separator so that the tab is located in the second coating portion of the separator.

[0038] Such a structure is shown diagrammatically in FIG.

[0039] Referring to FIG. 3, a unit cell 100 for a secondary battery has a structure in which an electrode plate 110 having a tab 111 formed on one side and a separator 120 are stacked.

[0040] At this time, in the separator 120, a second coating portion 123 of an insulating coating layer is formed on the base substrate 121 at one end of the separator at a portion overlapping with the electrode tab 111 based on the direction in which the electrode tab 111 is formed, and in the remaining portion, a first coating portion 122 of an organic / inorganic composite porous coating layer is formed on the base substrate 121 parallel to the second coating portion 123.

[0041] When the electrode plate 110 having the tab 111 formed thereon and the separator 120 are laminated, the tab 111 is located at the second coating portion 123 of the separator 120 .

[0042] Therefore, even if an insulating coating layer is not formed on the electrode plate 110 on which the tab 111 is formed, by forming an insulating coating layer on the separator 120, the effect of ensuring the safety of the battery cell can be ensured.

[0043] Alternatively, the tab may be formed on one or both sides of the electrode plate, and a second coating portion may be formed on one end of the separator at a portion overlapping with the tab based on the direction in which the tab is formed and the other end of the separator corresponding to the tab, and a first coating portion may be formed parallel to the second coating portion in the remaining portion, and the electrode may be stacked on the separator so that the tab is located at the second coating portion at one end or both ends.

[0044] Such a structure is shown diagrammatically in FIGS.

[0045] First, referring to FIG. 4, a unit cell 200 for a secondary battery has a structure in which an electrode plate 210 having a tab 211 formed on one side and a separator 220 are stacked.

[0046] At this time, a second coating portion 223 of an insulating coating layer is formed on the base substrate 221 at one end of the separator 220 that overlaps with the electrode tab 211 based on the direction in which the electrode tab 211 is formed and at the corresponding other end of the separator, and a first coating portion 222 of an organic / inorganic composite porous coating layer is formed on the base substrate 221 in the remaining portion in parallel to the second coating portion 223.

[0047] When the electrode plate 210 having the tab 211 formed thereon and the separator 220 are laminated, the tab 211 is located at the second coating portion 223 at one end of the separator 220 .

[0048] Referring to FIG. 5, a unit cell 300 for a secondary battery has a structure in which an electrode plate 310 having tabs 311 and 312 formed on both sides and a separator 320 are laminated.

[0049] At this time, a second coating portion 323 of an insulating coating layer is formed on the base substrate 321 at one end and the other end of the separator 320 where the separator overlaps with the electrode tabs 311, 312 based on the direction in which the electrode tabs 311, 312 are formed, and in the remaining portion, a first coating portion 322 of an organic / inorganic composite porous coating layer is formed on the base substrate 321 parallel to the second coating portion 323.

[0050] When the electrode plate 310 having the tabs 311 and 312 formed thereon and the separator 320 are laminated, the tabs 311 and 312 are located at the second coated portions 323 on both ends of the separator 320 .

[0051] Therefore, in any case, by including a second coating portion of the insulating coating layer at the portion where the separator contacts the tab, not only can the safety of the battery cell be ensured, but also, since no insulating coating is performed during slurry coating to manufacture the electrode plate, loss of electrode slurry due to poor alignment can be prevented.

[0052] In this case, the organic / inorganic composite porous coating layer of the first coating part is the same as the coating layer of a separator known as a conventional SRS, and may include, for example, inorganic particles and a binder polymer.

[0053] The inorganic particles may be, for example, high dielectric constant inorganic particles having a dielectric constant of 1 or more, 5 or more, preferably 10 or more, inorganic particles having piezoelectricity, inorganic particles having lithium ion transport ability, or a mixture thereof.

[0054] The binder polymer may be, but is not limited to, for example, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples of suitable materials include, but are not limited to, polyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, and mixtures thereof. Any material having the above-mentioned properties may be used alone or in combination.

[0055] The second coating portion is not limited to a material having insulating properties, but may be an insulating polymer coating layer, for example, a thermoplastic resin, a polyester resin, a polyolefin resin, an ethylene copolymer resin, or a polyvinylidene fluoride (PVdF)-based material, and more particularly, a polymer coating layer containing a PVdF-based material.

[0056] Meanwhile, the electrode plate of such a unit cell for a secondary battery may be a positive electrode plate or a negative electrode plate, but since the safety issue of such an electrode battery cell is mainly a problem that the negative electrode is formed larger than the positive electrode and lithium released from the negative electrode is formed in a protruding form on the positive electrode, the electrode plate of the unit cell including the separator having such an insulating coating layer formed thereon may be specifically a positive electrode plate.

[0057] In addition, the unit cell for a secondary battery does not have to include one electrode plate and one separator, but may include two or more electrode plates or two or more separators.

[0058] When the electrode plate is a positive electrode plate as described above, the secondary battery unit cell may further include a negative electrode plate, and may have a structure in which the separator is interposed between the positive electrode plate and the negative electrode plate.

[0059] On the other hand, when the electrode plate is a negative electrode plate, the secondary battery unit cell may further include a positive electrode plate, with the separator interposed between the positive electrode plate and the negative electrode plate.

[0060] At this time, as described above, the negative electrode plate may be larger than the positive electrode plate in four directions.

[0061] In addition, the secondary battery unit cell may further include an additional separator including a first coating portion and a second coating portion similar to the separator, and the additional separator may be laminated on the other side of the positive electrode plate or the negative electrode plate that does not face the separator.

[0062] Schematic diagrams of such structures are shown in Figures 6 and 7 below.

[0063] Referring first to FIG. 6, a unit cell 400 for a secondary battery includes a positive electrode plate 410 having a tab 411 formed on one side, a separator 420 having a first coating portion 422 of an organic / inorganic composite porous coating layer and a second coating portion 423 of an insulating coating layer formed on a base substrate 421, and further includes a negative electrode plate 430 having a tab 431 formed on one side, and an additional separator 440 having a base substrate 441, a first coating portion 442, and a second coating portion 443 formed in the same manner as the separator 420.

[0064] Here, the separator 420 is interposed between the positive electrode plate 410 and the negative electrode plate 430, and the additional separator 440 is laminated on the other side of the negative electrode plate 430 that does not face the separator 420.

[0065] In this case, the second coating portion 423 of the separator 420 and the second coating portion 443 of the additional separator 440 may be a polymer coating layer, as described above, and more specifically, may be a polymer coating layer containing a PVdF-based material.

[0066] Therefore, the second coating portion 423 of the separator 420 and the second coating portion 443 of the additional separator 440 are bonded to each other by subsequent lamination or the like and have excellent adhesive strength, thereby minimizing problems such as folding of the separator in the future and further improving battery safety.

[0067] Referring to FIG. 7, a unit cell 500 for a secondary battery includes a positive electrode plate 510 having a tab 511 formed on one side thereof, a separator 520, a negative electrode plate 530 having a tab 531 formed on one side thereof, and a separator 540 having the same structure as the separator 520.

[0068] 6 in that the second coating portion 523 of the separation membrane 520 and the second coating portion 543 of the additional separation membrane 540 are formed on both ends. In this case, the folding problem of the separation membrane can be more effectively solved.

[0069] Of course, a combination structure in which some of the separation membranes have the second coated portion formed only on one end and the remaining separation membranes have the second coated portion formed on both ends is also included in the scope of the present invention.

[0070] Meanwhile, according to another embodiment of the present invention, A method for manufacturing a unit cell for a secondary battery, comprising the steps of: (a) providing an electrode plate having tabs formed thereon; (b) forming a first coating portion of an organic / inorganic composite porous coating layer and a second coating portion of an insulating coating layer on at least one surface of a base substrate to manufacture a separator; and (c) laminating the electrode and a separator; Including, The first coated portion and the second coated portion are formed by simultaneously coating the first coated portion and the second coated portion.

[0071] In this case, the electrode plate may be a positive electrode plate or a negative electrode plate, and may be prepared by coating a current collector with an electrode slurry, drying, and rolling.

[0072] Since specific processes and materials are well known in the art, detailed description will be omitted in the present invention, and the present invention can be applied to electrode plates having configurations well known in the art.

[0073] In the separator that is manufactured later, the first and second coating portions may be formed separately, but may be formed by coating them simultaneously in consideration of the efficiency of the manufacturing process.

[0074] The coating method may include any conventionally known coating method, such as die coating, inkjet printing, spray coating, blade coating, and the like.

[0075] Therefore, when the organic / inorganic composite porous coating layer is formed, the insulating coating layer can also be formed, so that it can be formed in a simple manner without requiring a separate process.

[0076] Specific materials for the organic / inorganic composite porous coating layer and the insulating coating layer are as described above.

[0077] The electrodes and separator may then be stacked or laminated.

[0078] In addition, an additional electrode plate and an additional separator may also be stacked and laminated to manufacture a unit cell for a secondary battery.

[0079] Meanwhile, according to another embodiment of the present invention, there is provided an electrode assembly including the unit cell for a secondary battery, and a lithium secondary battery including the electrode assembly and a lithium salt non-aqueous electrolyte.

[0080] The above-mentioned configuration is well known in the art, and therefore a detailed description thereof will be omitted in this invention.

[0081] Those skilled in the art will appreciate that the present invention can be applied in various ways and modified within the scope of the present invention based on the above content. [Industrial Applicability]

[0082] As described above, in the secondary battery unit cell according to an embodiment of the present invention, the insulating coating layer is formed on a separator rather than an electrode, so that there is no loss of electrode slurry that would occur due to alignment during coating to form the insulating coating layer, and the safety of the battery cell that is intended to be obtained by forming the insulating coating layer can be ensured.

[0083] In addition, by applying the insulating coating layer to the separator as a polymer coating layer, the adhesive strength at both ends of the separator can be improved, which has the effect of reducing the problem of folding the separator.

Claims

1. A unit cell for a secondary battery, The secondary battery unit cell includes an electrode plate having a tab and a separator, The separator includes a first coating part having an organic / inorganic composite porous coating layer formed on at least one surface of a base substrate, and a second coating part having an insulating coating layer formed on at least one surface of the base substrate. The second coated portion is located at a position where the tab of the electrode plate is formed.

2. 2. The unit cell for a secondary battery according to claim 1, wherein the tab is formed on one side of the electrode plate, the second coating portion is formed on one end of the separator at a portion overlapping the tab based on a direction in which the tab is formed, and the first coating portion is formed parallel to the second coating portion in the remaining portion, and an electrode is stacked on the separator so that the tab is located in the second coating portion of the separator.

3. 3. The unit cell for a secondary battery according to claim 1, wherein the tab is formed on one or both sides of the electrode plate, the second coating portion is formed on one end of the separator at a portion overlapping with the tab based on a formation direction of the tab and the other end of the separator corresponding to the tab, and the first coating portion is formed parallel to the second coating portion in the remaining portion, and an electrode is stacked on the separator so that the tab is located at the second coating portion at one end or both ends.

4. The unit cell for a secondary battery according to claim 1 , wherein the electrode plate is a positive electrode plate.

5. The secondary battery unit cell according to claim 4 , further comprising a negative electrode plate, the separator being interposed between the positive electrode plate and the negative electrode plate.

6. 6. The unit cell for a secondary battery according to claim 5, wherein the negative electrode plate is larger than the positive electrode plate in four dimensions.

7. 7. The unit cell for a secondary battery according to claim 5 or 6, further comprising an additional separator including the first coating portion and the second coating portion in the same manner as the separator, and the additional separator is laminated on the other side of the positive electrode plate or the negative electrode plate that does not face the separator.

8. The unit cell for a secondary battery according to claim 7 , wherein the second coated portion of the separator and the second coated portion of the additional separator are bonded to each other.

9. The unit cell for a secondary battery according to claim 1 , wherein the insulating coating layer is a polymer coating layer containing a PVdF-based material.

10. An electrode assembly comprising the unit cell for a secondary battery according to claim 1 .

11. A lithium secondary battery comprising the electrode assembly according to claim 10 and a lithium salt non-aqueous electrolyte.

12. A method for producing a unit cell for a secondary battery according to any one of claims 1 to 9, comprising the steps of: (a) providing an electrode plate having tabs formed thereon; (b) forming a first coating portion of an organic / inorganic composite porous coating layer and a second coating portion of an insulating coating layer on at least one surface of a base substrate to manufacture a separator; and (c) laminating the electrodes and the separator; A method for producing a unit cell for a secondary battery, comprising the steps of:

13. The method for manufacturing a unit cell for a secondary battery according to claim 12 , wherein the first coated portion and the second coated portion are formed by simultaneous coating.

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