Electrode and manufacturing method therefor

Abstract

An electrode according to an embodiment of the present invention comprises: a base current collector; a porous current collector, which is layered on the base current collector and is thicker than the base current collector; and an active material layer, which is coated on the porous current collector and is thicker than the base current collector.

Description

Electrode and method for manufacturing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0099166, filed July 28, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to an electrode having an active material layer coated on a current collector and a method for manufacturing the same.

[0005] Secondary batteries typically have an electrode assembly housed within a case, and the electrode assembly housed within the case has a form in which a positive electrode, a separator, and a negative electrode are laminated at least once. In addition, 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.

[0006] The process for mass-producing positive or negative electrodes includes applying an active material slurry, in which a binder and a conductive agent are appropriately mixed, to at least one surface of an electrode current collector fabric transported in a roll-to-roll manner, and drying the applied active material slurry to form an active material layer. Through this series of processes, a laminate is formed in which an active material layer is coated on the electrode current collector.

[0007] Thereafter, the laminate can be cut at regular intervals to manufacture electrodes. Then, an electrode assembly can be manufactured by stacking multiple electrodes with a separator in between.

[0008] In this way, in the electrodes that make up the electrode assembly, the amount of active material coated on the current collector serves as a key factor in determining the capacity of the secondary battery. In other words, the thicker the active material layer coated on a given area of ​​the current collector, the greater the electrode capacity.

[0009] However, if the thickness of the active material layer is too thick compared to the thickness of the current collector, the lithium ion transfer path becomes long, causing lithium intercalation / deintercalation to occur in the active material located far from the current collector, and the movement of electrons through the current collector may be limited. In addition, the conductive material that provides the electrical path within the electrode is somewhat crowdedly distributed between the active material and the binder, and if the loading amount of the electrode layer is increased, the curvature of the electrical path increases, ultimately increasing the resistance. In other words, the problem of reduced electrode output occurs.

[0010] To address these issues, one could consider using a relatively thick porous current collector. However, this approach suffers from the problems of the active material slurry coated on the porous current collector flowing out, as well as the difficulty in notching and welding the electrode tabs.

[0011] The problem to be solved by the present invention is to provide an electrode having high capacity and output, and a method for manufacturing the same in which active material slurry does not flow out during the manufacturing process.

[0012] 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.

[0013] The above base current collector may include a holding portion on which the porous current collector is laminated; and a non-conductive portion connected to the holding portion and protruding outward from the porous current collector and the active material layer.

[0014] A portion of the above active material layer can be in contact with the base current collector through the porous current collector.

[0015] The thickness of the above active material layer may be greater than or equal to the thickness of the porous current collector.

[0016] 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.

[0017] A method for manufacturing an electrode according to an embodiment of the present invention may include a step of laminating a porous current collector thicker than the base current collector on a base current collector; and a step of coating an active material layer thicker than the base current collector on the porous current collector.

[0018] The step of coating the active material layer may include the step of applying an active material slurry to the porous current collector; and the step of drying the active material slurry while a portion of the active material slurry is in contact with the base current collector through the porous current collector to form the active material layer.

[0019] The thickness of the active material slurry applied to the porous current collector may be greater than the thickness of the porous current collector.

[0020] The above electrode manufacturing method may further include a step of rolling the base current collector, the porous current collector, and the active material layer.

[0021] The above base current collector may include a support portion on which the porous current collector is laminated; and a non-conductive portion connected to the support portion and protruding outward from the porous current collector and the active material layer. The electrode manufacturing method may further include a step of notching the non-conductive portion into an electrode tab.

[0022] According to a preferred embodiment of the present invention, since the porous current collector is thicker than the base current collector, the thickness of the active material layer can be increased without concern for a decrease in the output of the electrode, thereby increasing the capacity of the electrode. In other words, the electrode can have high capacity and output.

[0023] Additionally, the base current collector can prevent the active material slurry from flowing through the porous current collector during the electrode manufacturing process.

[0024] Additionally, a portion of the active material slurry may be dried to fill a plurality of holes provided in the porous current collector, thereby forming an active material layer. This allows the active material layer to be firmly bonded not only to the porous current collector but also to the base current collector, and the bonding strength between the porous current collector and the base current collector may also be enhanced.

[0025] In addition, the configurations according to preferred embodiments of the present invention may include effects that can be easily predicted by those skilled in the art.

[0026] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0027] Figure 1 is a plan view of an electrode according to a first embodiment of the present invention.

[0028] Figure 2 is a cross-sectional view taken along line A-A' of Figure 1.

[0029] Figure 3 is a cross-sectional view of an electrode according to a second embodiment of the present invention.

[0030] Figure 4 is a flowchart of an electrode manufacturing method according to a third embodiment of the present invention.

[0031] Figure 5 is a schematic diagram for explaining an electrode manufacturing method according to a third embodiment of the present invention.

[0032] Figure 6 is a plan view of the laminate shown in Figure 5.

[0033] Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited or restricted by the following examples.

[0034] In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification.

[0035] In addition, terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0036] FIG. 1 is a plan view of an electrode according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line A-A' of FIG. 1.

[0037] An electrode (1) according to the 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).

[0038] The base current collector (10) and the porous current collector (11) can serve to supply electrons provided from an external conductor (not shown) to the active material layer (30) or discharge electrons generated as a result of an electrode reaction to the external conductor.

[0039] The base current collector (10) and the porous current collector (20) are made of highly conductive metals, and any type of metal that does not cause chemical changes within the voltage range of the battery can be used. For example, copper, gold, iron, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used, but are not limited thereto.

[0040] A base current collector (10) may be adhered to one surface of the porous current collector (20), and an active material layer (30) may be adhered to the other surface of the porous current collector (20).

[0041] The thickness of the base collector (10) is not particularly limited, and for example, a thickness of 3 ㎛ to 500 ㎛ can be used.

[0042] The porous current collector (20) may have a three-dimensional mesh structure. Accordingly, the porous current collector (20) may be provided with a plurality of holes (21) (for convenience, only a single hole is illustrated in FIG. 2). The plurality of holes (21) may be formed uniformly or irregularly. However, the configuration of the porous current collector (20) is not limited thereto.

[0043] The active material layer (30) can be easily adhered to the porous current collector (20). The active material layer (30) may be referred to as an electrode mixture layer. The active material layer (30) includes an electrode active material and a binder, and may further include 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).

[0044] As the cathode active material, any active material commonly used in the cathode of a secondary battery can be used. For example, LiM x O y (M = Co, Ni, Mn, Co a Ni b Mn c) such as lithium transition metal composite oxides (e.g., lithium manganese composite oxides such as LiMn2O4, lithium nickel oxides such as LiNiO2, lithium cobalt oxides such as LiCoO2, and those in which some of the manganese, nickel, and cobalt in these oxides are replaced with other transition metals, or vanadium oxides containing lithium, etc.) or chalcogen compounds (e.g., manganese dioxide, titanium disulfide, molybdenum disulfide, etc.) can be used.

[0045] As the negative active material, an active material commonly used in the negative electrode of a secondary battery can be used. For example, a lithium adsorption material such as lithium alloy, carbon, petroleum coke, activated carbon, graphite, or other carbons can be used, and also TiO2, SnO2, or Li4Ti5O having a potential of less than 2 V with respect to lithium. 12 Metal oxides such as, but not limited to, may be used.

[0046] For electrode active materials, the binder can be appropriately used in an amount of 1 to 10 wt% based on the total weight of the electrode active material, and the conductive material can be appropriately used in an amount of 1 to 30 wt%. Examples of binders that can be used include aqueous binders such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyvinylacetate, polyethylene oxide, polypyrrolidone, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid (PAA), carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR).

[0047] Carbon black is typically used as a conductive material. Current commercially available conductive materials include acetylene black (e.g., Chevron Chemical Company or Gulf Oil Company), Ketjen Black EC (e.g., Armak Company), Vulcan XC-72 (e.g., Cabot Company), and Super P (MMM). Linear conductive materials such as carbon nanotubes and carbon (nano) fibers are also available.

[0048] The active material layer (30) can be formed on the porous current collector (20) by a generally used method. For example, an electrode active material can be mixed with a binder and a solvent, and optionally a conductive material and a dispersant, stirred to prepare an active material slurry, and then the active material slurry can be applied to one surface of the porous current collector (20), compressed, and dried. The method for applying the active material slurry to the current collector is not particularly limited, and for example, it can be applied by a doctor blade, dipping, brushing, or the like.

[0049] The method for removing the solvent or dispersion medium is not particularly limited, but the solvent or dispersion medium may be dried so as to evaporate as quickly as possible within a speed range that does not cause stress concentration to occur, causing cracks in the active material layer (30), or the active material layer (30) to peel off from the porous current collector (20).

[0050] A part (30a) of the active material layer (30) can be in contact with the base current collector (10) through the porous current collector (20). More specifically, the active material layer (30) is applied on the porous current collector (20) in the form of an active material slurry, and a part of the active material slurry can be filled in a plurality of holes (21) provided in the porous current collector (20). In addition, the active material slurry filled in the plurality of holes can reach one surface of the base current collector (10) and be in contact with the base current collector (10). The one surface of the base current collector (10) means a surface on which the porous current collector (20) is laminated.

[0051] Accordingly, the active material layer (30) can be firmly bonded not only to the porous current collector (20) but also to the base current collector (10). In addition, the bonding strength between the porous current collector (20) and the base current collector (10) can also be improved. Accordingly, the active material layer (30) can be prevented from being peeled off due to repeated expansion and contraction caused by repeated charging and discharging of the battery.

[0052] If the electrode (1) does not include a base current collector (10), there is a risk that the active material slurry applied on the porous current collector (20) may flow through the multiple holes (21) of the porous current collector (20). The base current collector (10) can prevent this risk.

[0053] The thickness (t2) of the porous current collector (20) may be thicker than the thickness (t1) of the base current collector (10). Accordingly, since the thickness (t2) of the porous current collector (20) can be formed sufficiently thick, even if the thickness (t3) of the active material layer (30) is increased to increase the capacity of the electrode (1), the output of the electrode (1) can be prevented from decreasing. That is, by providing the porous current collector (20), the thickness (t1+t2) of the current collector (10)(20) can be prevented from becoming excessively thinner compared to the thickness (t3) of the active material layer (30).

[0054] The thickness (t3) of the active material layer (30) may be thicker than the thickness (t1) of the base current collector (10). The thickness (t3) of the active material layer (30) may be greater than or equal to the thickness (t2) of the porous current collector (20). Accordingly, the thickness (t3) of the active material layer (30) can be formed sufficiently thick, thereby increasing the capacity of the electrode (1).

[0055] Meanwhile, the base current collector (10) may include a holding portion (11) on which a porous current collector (20) is laminated, and a non-conductive portion (12) connected to the holding portion (11) and protruding outward from the porous current collector (20) and the active material layer (30).

[0056] The maintenance portion (11) may be an area that overlaps with the porous current collector (20) and the active material layer (30) in the thickness direction of the electrode (1).

[0057] The non-coated portion (12) may be a region that does not overlap with the porous current collector (20) and the active material layer (30) in the thickness direction of the electrode (1). The non-coated portion (12) may be notched with an electrode tab having a preset shape. Since the non-coated portion and the electrode tab are substantially the same, the drawing reference numerals for both configurations are hereinafter identically indicated as '12'.

[0058] Therefore, the electrode tab (12) can be easily formed by notching the base current collector (10) having a relatively thin thickness. If the electrode tab is to be formed by notching the porous current collector (20), the notching process will not be easy due to the thick thickness of the porous current collector (20).

[0059] In addition, when manufacturing an electrode assembly by stacking a plurality of electrodes (1), the electrode tabs (12) of the plurality of electrodes (1) can be welded together. Since each electrode tab (12) is formed by notching the base current collector (10), it can have a thin thickness, and therefore, the plurality of electrode tabs (12) can be easily welded. If each electrode tab is formed by notching the porous current collector (20), welding between the plurality of electrode tabs will not be easy due to the thick thickness of the electrode tab.

[0060] Figure 3 is a cross-sectional view of an electrode according to a second embodiment of the present invention.

[0061] Below, we will omit any overlapping information from what was previously explained and focus on explaining the differences.

[0062] In the electrode according to the present embodiment, a pair of porous current collectors (20) and active material layers (30) may be provided.

[0063] In more detail, the porous current collector (20) may include a first porous current collector (20a) laminated on one surface of a base current collector (10) and a second porous current collector (20b) laminated on the other surface of the base current collector (10).

[0064] In addition, 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 outer surface of each porous current collector (20a)(20b) means a surface located opposite the base current collector (10).

[0065] By this configuration, the capacity and output of the electrode according to the present embodiment can be further improved.

[0066] FIG. 4 is a flowchart of an electrode manufacturing method according to a third embodiment of the present invention, FIG. 5 is a schematic diagram for explaining an electrode manufacturing method according to a third embodiment of the present invention, and FIG. 6 is a plan view of the laminate illustrated in FIG. 5.

[0067] The electrode manufacturing method according to the third embodiment of the present invention (hereinafter, “manufacturing method”) may include a step (S10) (hereinafter, “lamination step”) of laminating a porous current collector (20) on a base current collector (10), and a step (S20) (hereinafter, “coating step”) of coating an active material layer (30) on the porous current collector (20).

[0068] In Fig. 4, the lamination step (S10) and the coating step (S20) are illustrated as being performed sequentially. However, this is not limited to the present invention, and 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.

[0069] In the lamination step (S10), the base current collector (10) and the porous current collector (20) may each be supplied in the form of sheets having a constant width. At this time, the width (W1) of the base current collector (10) may be wider than the width of the porous current collector (20). In addition, as described above, the porous current collector (20) may be thicker than the base current collector (10).

[0070] The porous current collector (20) can be supplied so as to be laminated on at least one side of the base current collector (10). In FIG. 5, a single porous current collector (20) is supplied so as to be laminated on one side of the base current collector (10), but it is also possible for a pair of porous current collectors (20) to be supplied so as to be laminated on both sides of the base current collector (10).

[0071] The base collector (10) and the porous collector (20) can run at the same speed.

[0072] The coating step (S20) may include a step of applying an active material slurry to a porous current collector (20) (hereinafter, the 'application step') and a step of drying the active material slurry to form an active material layer (30) (hereinafter, the 'drying step'). Since the active material slurry and the active material layer are substantially the same, the drawing reference numerals for both components are hereinafter the same as '30'.

[0073] In the above application step, the coater (110) can continuously or periodically apply the active material slurry (30) to the outer surface of the moving porous current collector (20).

[0074] The thickness of the active material slurry (30) applied to the porous current collector (20) may be thicker than the thickness (t1) of the base current collector (10). The thickness of the active material slurry (30) may be greater than or equal to the thickness (t2) of the porous current collector (20).

[0075] The width (W2) of the active material slurry (30) applied to the porous current collector (20) may be the same as or similar to the width of the porous current collector (20). Accordingly, the width (W1) of the base current collector (10) may be wider than the width (W2) of the active material slurry (30). A portion of the base current collector (10) that protrudes beyond the active material slurry (30) may be defined as a non-coated portion (12).

[0076] In the above drying step, the active material slurry (30) applied to the porous collector (20) can be dried while passing through the drying chamber (120), and an active material layer (30) can be formed.

[0077] When the active material slurry (30) is dried, a portion of the active material slurry (30) may be in contact with the base current collector (10) through the porous current collector (20). That is, the active material slurry (30) may be dried in a state where a portion thereof is filled in a plurality of holes (21) provided in the porous laminate (20). Accordingly, the active material layer (30) may be firmly bonded not only to the porous current collector (20) but also to the base current collector (10). In addition, the bonding strength between the porous current collector (20) and the base current collector (10) may also be improved.

[0078] When the above drying step is completed, a laminate (1a) in which a base current collector (10), a porous current collector (20), and an active material layer (30) are laminated can be manufactured.

[0079] 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, “rolling step”).

[0080] In the rolling step (S30), the laminate (1a) can be rolled while passing between a pair of rolling rolls (130). As a result, the base current collector (10), the porous current collector (20), and the active material layer (30) can be more firmly bonded to each other.

[0081] The above manufacturing method may further include a step (S40) of notching the non-conductive portion (12) of the base current collector (10) with an electrode tab (12) (hereinafter, “notching step”).

[0082] A notching unit (not shown) can form an electrode tab (12) by notching a non-conductive portion (12) into a predetermined shape. The notching unit can notch not only the non-conductive portion (12) but also a portion of the edge of the retaining portion (11). The notching unit can perform notching along an imaginary notching line (NL), and the outer portion of the notching line (NL) can be cut off and removed.

[0083] The electrode tab (12) may be a portion that is not cut off from the non-conductive portion (12) and remains. The electrode tab (12) may be formed at predetermined intervals along the length direction of the laminate (1a).

[0084] Thereafter, in a subsequent process, the laminate (1a) on which the electrode tab (12) is formed can be cut at regular intervals to be processed into an electrode (1).

[0085] The above description is merely an example of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present invention.

[0086] Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of ​​the present invention but to explain it, and the scope of the technical idea of ​​the present invention is not limited by these embodiments.

[0087] The scope of protection of the present invention should be interpreted by the claims below, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

[0088] [Explanation of symbols]

[0089] 1: Electrode 1a: Laminate

[0090] 10: Base collector 11: Maintenance section

[0091] 12: Non-conductive, electrode tab 20: Porous current collector

[0092] 30: Active material layer, active material slurry

Claims

1. Base collector; A porous collector laminated on the base collector and thicker than the base collector; and An electrode comprising an active material layer coated on the porous current collector and thicker than the base current collector.

2. In paragraph 1, The above base collector, A maintenance part on which the above porous collector is laminated; and An electrode connected to the above-mentioned maintenance portion and including a non-conductive portion protruding outward from the porous current collector and active material layer.

3. In paragraph 1, An electrode in which a portion of the active material layer is in contact with the base current collector through the porous current collector.

4. In paragraph 1, An electrode in which the thickness of the above active material layer is greater than or equal to the thickness of the above porous current collector.

5. In paragraph 1, The above porous collector, A first porous current collector laminated on one side of the above base current collector; and Including a second porous collector laminated on the other side of the base collector, The above active material layer is, A first active material layer coated on the outer surface of the first porous collector; and An electrode comprising a second active material layer coated on the outer surface of the second porous current collector.

6. A step of laminating a porous collector thicker than the base collector on the base collector; and A method for manufacturing an electrode, comprising a step of coating a layer of active material thicker than the base current collector on the porous current collector.

7. In paragraph 6, The step of coating the above active material layer is: A step of applying an active material slurry to the porous collector; and A method for manufacturing an electrode, comprising a 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 through the porous current collector.

8. In paragraph 7, A method for manufacturing an electrode in which the thickness of the active material slurry applied to the porous current collector is greater than or equal to the thickness of the porous current collector.

9. In paragraph 6, A method for manufacturing an electrode further comprising a step of rolling the base current collector, the porous current collector, and the active material layer.

10. In paragraph 6, The above base collector, A maintenance part on which the above porous collector is laminated; and It includes a non-conductive portion that is connected to the above-mentioned maintenance portion and protrudes outward from the porous current collector and active material layer, An electrode manufacturing method further comprising a step of notching the above-mentioned portion with an electrode tab.

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