Electrodes and methods for manufacturing the same

Abstract

An electrode according to an embodiment of the present invention may include a base current collector, a porous current collector laminated on the base current collector and thicker than the base current collector, and an active material layer coated on the porous current collector and thicker than the base current collector.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0099166 filed on July 28, 2023, and all the contents disclosed in the document of the Korean Patent Application are incorporated herein by reference in their entirety.

[0002] The present invention relates to an electrode in which an active material layer is coated on a current collector and a method for manufacturing the same.

Background Art

[0003] A secondary battery generally has a form in which an electrode assembly is housed in a case, and the electrode assembly housed in the case has a form in which a positive electrode, a separator, and a negative electrode are laminated at least once or more. Also, the positive electrode and the negative electrode may include a current collector and an active material layer coated on at least one surface of the current collector.

[0004] The process for mass-producing a positive electrode or a negative electrode includes a process of applying an active material slurry in which a binder and a conductive material are appropriately mixed onto at least one surface of a raw sheet of an electrode current collector transferred in a roll-to-roll manner, and a process of drying the applied active material slurry to form an active material layer. Through such a series of processes, a laminate in which an active material layer is coated on an electrode current collector is formed. <​​​​​​​​​​However, if the active material layer is too thick compared to the current collector, the lithium ion transfer path becomes longer, leading to lithium intercalation / deintercalation to the active material far from the current collector, which can restrict electron movement through the current collector. Furthermore, while the conductive material providing the electrical pathways within the electrodes is distributed somewhat randomly between the active material and the binder, increasing the loading amount of the electrode layer increases the curvature of the electrical pathways, ultimately increasing resistance. This results in a decrease in electrode output.

[0008] To solve these problems, one possible approach is to use a porous current collector with a relatively high thickness. However, this approach has problems not only with the active material slurry coating the porous current collector dripping, but also with the difficulty of notching and welding the electrode tabs. [Overview of the project] [Problems that the invention aims to solve]

[0009] One problem that this invention aims to solve is to provide an electrode with high capacity and output, and in which the active material slurry does not drip during the manufacturing process, as well as a method for manufacturing the same. [Means for solving the problem]

[0010] An electrode according to an embodiment of the present invention may include a base current collector, a porous current collector laminated on the base current collector and thicker than the base current collector, and an active material layer coated on the porous current collector and thicker than the base current collector.

[0011] The base current collector may include a support portion on which the porous current collector is laminated, and a plain portion connected to the support portion and protruding outward from the porous current collector and the active material layer.

[0012] A portion of the active material layer can come into contact with the base current collector via the porous current collector.

[0013] The thickness of the active material layer can be greater than or equal to the thickness of the porous current collector.

[0014] The porous current collector may include a first porous current collector laminated on one surface of the base current collector and a second porous current collector laminated on the other surface of the base current collector. The active material layer may include a first active material layer coated on the outer surface of the first porous current collector and a second active material layer coated on the outer surface of the second porous current collector.

[0015] A method for manufacturing an electrode according to an embodiment of the present invention may include the steps of laminating a porous current collector thicker than the base current collector onto a base current collector, and coating the porous current collector with an active material layer thicker than the base current collector.

[0016] The step of coating the active material layer may include the steps of applying an active material slurry to the porous current collector and drying the active material slurry to form the active material layer while a portion of the active material slurry is in contact with the base current collector via the porous current collector.

[0017] The thickness of the active material slurry applied to the porous current collector can be greater than or equal to the thickness of the porous current collector.

[0018] The method for manufacturing the electrode may further include the step of rolling the base current collector, the porous current collector, and the active material layer.

[0019] The base current collector may include a support portion on which the porous current collector is laminated, and a blank portion connected to the support portion and protruding outward from the porous current collector and the active material layer. The method for manufacturing the electrode may further include the step of cutting out the blank portion as an electrode tab. [Effects of the Invention]

[0020] According to a preferred embodiment of the present invention, since the porous current collector is thicker than the base current collector, there is no risk of reducing the output of the electrode, and the thickness of the active material layer can be increased, thereby increasing the capacity of the electrode. That is, the electrode can have a high capacity and output.

[0021] Also, the base current collector can prevent the active material slurry from dripping through the porous current collector during the manufacturing process of the electrode.

[0022] Further, a part of the active material slurry can be dried in a state of being filled in a large number of holes provided in the porous current collector to form an active material layer. Thereby, the active material layer can be firmly bonded not only to the porous current collector but also to the base current collector, and the bonding force between the porous current collector and the base current collector can be improved.

[0023] In addition, it can include effects that can be easily predicted by those skilled in the art from the configuration according to the preferred embodiment of the present invention.

Brief Description of the Drawings

[0024] The following drawings attached to this specification illustrate the preferred embodiments of the present invention and serve to further understand the technical idea of the present invention together with the detailed description of the invention to be described later. The present invention should not be construed as being limited only to the matters described in such drawings.

[0025] [Figure 1] It is a plan view of an electrode according to the first embodiment of the present invention. [Figure 2] It is a cross-sectional view taken along line A-A' of FIG. 1. [Figure 3] It is a cross-sectional view of an electrode according to the second embodiment of the present invention. [Figure 4] It is a flowchart of a method for manufacturing an electrode according to the third embodiment of the present invention. [Figure 5] It is a schematic diagram for explaining the method for manufacturing an electrode according to the third embodiment of the present invention. [Figure 6]Figure 5 is a plan view of the laminated structure. [Modes for carrying out the invention]

[0026] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings, so as to be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in a variety of different forms and is not limited or restricted by the following embodiments.

[0027] In order to clearly explain the present invention, detailed descriptions of related prior art that are irrelevant to the description or that could obscure the gist of the invention have been omitted. In this specification, when assigning reference numerals to components in the drawings, the same or similar reference numerals are used for components that are the same or similar throughout the specification.

[0028] Furthermore, the terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0029] Figure 1 is a plan view of an electrode according to a first embodiment of the present invention, and Figure 2 is a cross-sectional view along line A-A' in Figure 1.

[0030] An electrode 1 according to a first embodiment of the present invention may include a base current collector 10, a porous current collector 20 laminated on the base current collector 10, and an active material layer 30 coated on the porous current collector 20.

[0031] The base current collector 10 and the porous current collector 20 can either supply electrons from an external conductor (not shown) to the active material layer 30, or discharge electrons generated as a result of the electrode reaction to the external conductor.

[0032] The base current collector 10 and the porous current collector 20 can be made of any type of metal, as long as they are highly conductive and do not undergo chemical changes within the battery voltage range. For example, copper, gold, iron, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, or silver can be used, but are not limited to these.

[0033] A base current collector 10 can be bonded to one surface of the porous current collector 20, and an active material layer 30 can be bonded to the other surface of the porous current collector 20.

[0034] The thickness of the base current collector 10 is not particularly limited; for example, a thickness of 3 μm to 500 μm can be used.

[0035] The porous current collector 20 may have a three-dimensional mesh structure. Therefore, the porous current collector 20 may be provided with numerous holes 21 (for convenience, only a single hole is shown in Figure 2). The numerous holes 21 may be formed uniformly or irregularly. However, the configuration of the porous current collector 20 is not limited to this.

[0036] The active material layer 30 can be easily bonded onto the porous current collector 20. The active material layer 30 may be referred to as an electrode mixture layer. The active material layer 30 comprises an electrode active material and a binder, and may further contain a conductive material as needed. The electrode active material may be a positive electrode active material or a negative electrode active material depending on the polarity of the electrode 1.

[0037] As the positive electrode active material, any active material commonly used in the positive electrode of a secondary battery can be used. For example, LiM x O y (M=Co, Ni, Mn, Co a Ni b Mn cLithium transition metal composite oxides such as ) (e.g., lithium manganese composite oxides such as LiMn2O4, lithium nickel oxides such as LiNiO2, lithium cobalt oxides such as LiCoO2, and those oxides in which some of the manganese, nickel, and cobalt are replaced with other transition metals, or vanadium oxide containing lithium, etc.) or chalcogen compounds (e.g., manganese dioxide, titanium disulfide, molybdenum disulfide, etc.) can be used.

[0038] As the negative electrode active material, active materials commonly used in the negative electrodes of secondary batteries can be used. For example, lithium-adsorbing materials such as lithium alloys, carbon, petroleum coke, activated carbon, graphite, or other carbons can be used, as well as TiO2, SnO2, or Li4Ti5O2, which have a potential of less than 2V relative to lithium. 12 Metal oxides such as those mentioned above can be used, but are not limited to them.

[0039] For electrode active materials, the binder can be appropriately used in an amount of 1% to 10% by weight relative to the total weight of the electrode active material, and the conductive material can be appropriately used in an amount of 1% to 30% by weight. Examples of usable binders include water-based binders such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyvinyl acetate, polyethylene oxide, polypyrrolidone, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid (PAA), carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR).

[0040] Generally, carbon black can be used as a conductive material. Currently, commercially available conductive materials include acetylene black (manufactured by Chevron Chemical Company or Gulf Oil Company, etc.), Ketjen Black EC (manufactured by Armak Company, etc.), Vulcan XC-72 (manufactured by Cabot Company, etc.), and Super P (manufactured by MMM). There are also linear conductive materials such as carbon nanotubes and carbon (nano)fibers.

[0041] The active material layer 30 can be formed on the porous current collector 20 by a commonly used method. For example, it can be produced by mixing an electrode active material with a binder and a solvent, and optionally a conductive material and a dispersant, stirring to produce an active material slurry, then applying the active material slurry to one surface of the porous current collector 20, compressing it, and drying it. The method of applying the active material slurry to the current collector is not particularly limited and can be applied by methods such as using a doctor blade, dipping, or brushing.

[0042] The method for removing the solvent or dispersion medium is not particularly limited, but it is preferable that the solvent or dispersion medium be dried so that it volatilizes quickly within a speed range that does not cause stress concentration and cracking in the active material layer 30, or cause the active material layer 30 to peel off from the porous current collector 20.

[0043] A portion 30a of the active material layer 30 can come into contact with the base current collector 10 via the porous current collector 20. More specifically, since the active material layer 30 is applied onto the porous current collector 20 in the form of an active material slurry, a portion of the active material slurry can fill the numerous holes 21 provided in the porous current collector 20. Furthermore, the active material slurry filling the numerous holes can reach one surface of the base current collector 10 and come into contact with it. The surface of the base current collector 10 refers to the surface on which the porous current collector 20 is laminated.

[0044] This allows the active material layer 30 to be firmly bonded not only to the porous current collector 20 but also to the base current collector 10. Furthermore, the bonding strength between the porous current collector 20 and the base current collector 10 can be improved. Therefore, it is possible to prevent the active material layer 30 from peeling off due to repeated expansion and contraction caused by repeated charging and discharging of the battery.

[0045] If electrode 1 does not include the base current collector 10, the active material slurry coated on the porous current collector 20 may drip through the numerous holes 21 in the porous current collector 20. The base current collector 10 can prevent such a risk.

[0046] The thickness t2 of the porous current collector 20 may be thicker than the thickness t1 of the base current collector 10. This allows the porous current collector 20 to be formed with a sufficiently thick thickness t2, and prevents a decrease in the output of electrode 1 even when the thickness t3 of the active material layer 30 is increased to increase the capacitance of electrode 1. In other words, by providing the porous current collector 20, it is possible to prevent the thickness t1+t2 of current collectors 10 and 20 from becoming excessively thin compared to the thickness t3 of the active material layer 30.

[0047] The thickness t3 of the active material layer 30 may be greater than the thickness t1 of the base current collector 10. The thickness t3 of the active material layer 30 may also be greater than or equal to the thickness t2 of the porous current collector 20. This allows the thickness t3 of the active material layer 30 to be formed to be sufficiently thick, thereby increasing the capacitance of the electrode 1.

[0048] On the other hand, the base current collector 10 may include a maintenance portion 11 on which porous current collectors 20 are stacked, and a plain portion 12 connected to the maintenance portion 11 and protruding outward from the porous current collectors 20 and the active material layer 30.

[0049] The maintenance portion 11 may be a region that overlaps with the porous current collector 20 and the active material layer 30 in the thickness direction of the electrode 1.

[0050] The blank portion 12 may be an area in the thickness direction of the electrode 1 that does not overlap with the porous current collector 20 and the active material layer 30. The blank portion 12 can be cut out as an electrode tab having a predetermined shape. The blank portion and the electrode tab are substantially the same, and in the following, the reference numerals for both configurations will be the same as "12".

[0051] Therefore, the electrode tab 12 can be easily formed by cutting a notch in the base current collector 10, which has a relatively thin thickness. However, if one attempts to form an electrode tab by cutting a notch in the porous current collector 20, the thick thickness of the porous current collector 20 makes the cutting process difficult.

[0052] Furthermore, when manufacturing an electrode assembly by stacking multiple electrodes 1, the electrode tabs 12 of multiple electrodes 1 can be welded together. Each electrode tab 12 is formed by cutting a notch in the base current collector 10 and can have a thin thickness, so that multiple electrode tabs 12 can be easily welded together. If each electrode tab is formed by cutting a notch in the porous current collector 20, the thickness of the electrode tabs makes welding between multiple electrode tabs difficult.

[0053] Figure 3 is a cross-sectional view of an electrode according to a second embodiment of the present invention.

[0054] The following explanation will omit any content that overlaps with the above and will focus on the differences.

[0055] In the case of electrodes according to this embodiment, one pair each of porous current collectors 20 and active material layers 30 can be provided.

[0056] More specifically, the porous current collector 20 may include a first porous current collector 20a laminated on one surface of the base current collector 10 and a second porous current collector 20b laminated on the other surface of the base current collector 10.

[0057] Furthermore, the active material layer 30 may include a first active material layer 30a coated on the outer surface of the first porous current collector 20a and a second active material layer 30b coated on the outer surface of the second porous current collector 20b. The other surface of each porous current collector 20a, 20b means the surface located opposite the base current collector 10.

[0058] With this configuration, the capacitance and output of the electrodes according to this embodiment can be further improved.

[0059] Figure 4 is a flowchart of the method for manufacturing an electrode according to the third embodiment of the present invention, Figure 5 is a schematic diagram illustrating the method for manufacturing an electrode according to the third embodiment of the present invention, and Figure 6 is a plan view of the laminate shown in Figure 5.

[0060] A method for manufacturing an electrode according to a third embodiment of the present invention (hereinafter referred to as the "manufacturing method") may include the steps of laminating a porous current collector 20 on a base current collector 10 (S10) (hereinafter referred to as the "lamination step") and coating the porous current collector 20 with an active material layer 30 (S20) (hereinafter referred to as the "coating step").

[0061] Figure 4 illustrates that the lamination step (S10) and the coating step (S20) are performed in sequence. However, this is not the only option; the coating step (S20) may be performed before the lamination step (S10), or the lamination step (S10) and the coating step (S20) may be performed simultaneously.

[0062] In the lamination step (S10), the base current collector 10 and the porous current collector 20 can each be supplied in sheet form having a predetermined width. Here, the width W1 of the base current collector 10 can be wider than the width of the porous current collector 20. Also, as described above, the porous current collector 20 can be thicker than the base current collector 10.

[0063] The porous current collector 20 can be supplied so as to be laminated on at least one surface of the base current collector 10. Figure 5 illustrates that a single porous current collector 20 is supplied so as to be laminated on one surface of the base current collector 10, but it goes without saying that a pair of porous current collectors 20 can also be supplied so as to be laminated on both sides of the base current collector 10.

[0064] The base current collector 10 and the porous current collector 20 can travel at the same speed.

[0065] The coating step (S20) may include a step of applying an active material slurry to the porous current collector 20 (hereinafter referred to as the "coating step") and a step of drying the active material slurry to form an active material layer 30 (hereinafter referred to as the "drying step"). The active material slurry and the active material layer are substantially the same, and in the following, the reference numerals in the drawings for both components will be the same as "30".

[0066] In the coating step, the coater 110 can continuously or periodically apply the active material slurry 30 to the outer surface of the porous current collector 20 while it is in motion.

[0067] The thickness t3 of the active material slurry 30 applied to the porous current collector 20 may be greater than the thickness t1 of the base current collector 10. The thickness t3 of the active material slurry 30 may be greater than or equal to the thickness t2 of the porous current collector 20.

[0068] The width W2 of the active material slurry 30 applied to the porous current collector 20 can be the same as or similar to the width of the porous current collector 20. Therefore, the width W1 of the base current collector 10 can be wider than the width W2 of the active material slurry 30. In the base current collector 10, the portion protruding from the active material slurry 30 can be defined as the plain portion 12.

[0069] In the drying step, the active material slurry 30 applied to the porous current collector 20 can be dried while passing through the drying chamber 120, thereby forming the active material layer 30.

[0070] When the active material slurry 30 dries, a portion of the active material slurry 30 can remain in contact with the base current collector 10 via the porous current collector 20. That is, the active material slurry 30 can dry with a portion of it filling the numerous holes 21 provided in the porous laminate 20. This allows the active material layer 30 to bond firmly not only to the porous current collector 20 but also to the base current collector 10. Furthermore, the bonding strength between the porous current collector 20 and the base current collector 10 can also be improved.

[0071] Once the drying step is complete, a laminate 1a can be manufactured in which the base current collector 10, the porous current collector 20, and the active material layer 30 are laminated together.

[0072] The above manufacturing method may further include a step (S30) of rolling the base current collector 10, the porous current collector 20, and the active material layer 30 (hereinafter referred to as the "rolling step").

[0073] In the rolling step (S30), the laminate 1a can be rolled while passing between a pair of rolling rolls 130. This allows the base current collector 10, the porous current collector 20, and the active material layer 30 to bond more firmly to each other.

[0074] The above manufacturing method may further include the step (S40) of cutting out the plain portion 12 of the base current collector 10 as an electrode tab 12 (hereinafter referred to as the "cutting step").

[0075] A notching unit (not shown) can cut out the blank portion 12 into a predetermined shape to form an electrode tab 12. The notching unit can also cut out not only the blank portion 12 but also a portion of the edge side of the retaining portion 11. The notching unit can make a notch along a virtual notch line NL, and the portion outside the notch line NL can be cut out and removed.

[0076] The electrode tabs 12 may be the remaining portion that is not cut out from the plain portion 12. The electrode tabs 12 may be formed at predetermined intervals along the longitudinal direction of the laminate 1a.

[0077] Subsequently, in a later process, the laminate 1a on which the electrode tabs 12 are formed can be cut into predetermined lengths and processed into electrodes 1.

[0078] The above description is merely illustrative of the technical concept of the present invention, and any person with ordinary skill in the art to which the present invention belongs can make various modifications and alterations without departing from the essential characteristics of the present invention.

[0079] Therefore, the embodiments disclosed in this invention are for illustrative purposes only and not to limit the technical concept of the invention, and the scope of the technical concept of the invention is not limited by such embodiments.

[0080] The scope of protection of this invention shall be interpreted in accordance with the following claims, and all technical ideas within an equivalent scope shall be interpreted as being included within the scope of the rights of this invention. [Explanation of symbols]

[0081] 1 electrode 1a Laminate 10 Base current collector 11 Maintenance Department 12 Plain area, electrode tab 20. Porous current collector 30 Active material layer, active material slurry

Claims

1. Base current collector and A porous current collector, which is laminated on the base current collector and is thicker than the base current collector, An electrode comprising a porous current collector coated with an active material layer thicker than the base current collector.

2. The aforementioned base current collector is The retention section on which the porous current collectors are stacked, The electrode according to claim 1, comprising a plain portion connected to the maintenance portion and protruding outward from the porous current collector and the active material layer.

3. The electrode according to claim 1, wherein a portion of the active material layer is in contact with the base current collector via the porous current collector.

4. The electrode according to claim 1, wherein the thickness of the active material layer is equal to or greater than the thickness of the porous current collector.

5. The porous current collector is A first porous current collector is laminated on one surface of the base current collector, It includes a second porous current collector laminated on the other side of the base current collector, The aforementioned active material layer is A first active material layer coated on the outer surface of the first porous current collector, The electrode according to claim 1, comprising a second active material layer coated on the outer surface of the second porous current collector.

6. The steps include: stacking a porous current collector thicker than the base current collector on the base current collector; A method for manufacturing an electrode, comprising the step of coating the porous current collector with an active material layer thicker than the base current collector.

7. The step of coating the active material layer is, The steps include applying an active material slurry to the porous current collector, A method for manufacturing an electrode according to claim 6, comprising the step of drying the active material slurry to form the active material layer while a portion of the active material slurry is in contact with the base current collector via the porous current collector.

8. The method for manufacturing an electrode according to claim 7, wherein the thickness of the active material slurry applied to the porous current collector is equal to or greater than the thickness of the porous current collector.

9. The method for manufacturing an electrode according to claim 6, further comprising the step of rolling the base current collector, the porous current collector, and the active material layer.

10. The aforementioned base current collector is The retention section on which the porous current collectors are stacked, It includes a plain portion connected to the maintenance portion and protruding outward from the porous current collector and the active material layer, The method for manufacturing an electrode according to claim 6, further comprising the step of cutting out the plain portion to be used as an electrode tab.

Images