Method for manufacturing electrode, electrode, and secondary battery comprising same

Abstract

The present invention relates to a method for manufacturing an electrode, an electrode, and a secondary battery comprising the electrode. The method comprises the steps of: applying an electrode active material slurry to one surface or both surfaces of an electrode current collector; drying the electrode active material slurry to form an electrode active material layer; and rolling the electrode active material layer, wherein the electrode active material slurry contains an electrode active material having an average particle diameter (D50) of 4 µm or less, and the rolling is performed using a rolling roll having a surface roughness Ry value of 1 µm or more. Accordingly, it is possible to provide an electrode having improved electrolyte impregnation and a high-performance secondary battery.

Description

Method for manufacturing an electrode, electrode, and secondary battery including the same

[0001] Cross-citation with related application(s)

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2025-0005336 filed January 14, 2025 and Korean Patent Application No. 10-2025-0208189 filed December 23, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of the specification.

[0003] The present invention relates to a method for manufacturing an electrode for a secondary battery, an electrode, and a secondary battery including the same. More specifically, the invention relates to a method for manufacturing an electrode including an electrode active material having an average particle size (D50) of 4 μm or less, comprising the step of rolling using a rolling roll having a surface roughness Ry value of 1 μm or more.

[0004] In modern society, as the use of portable devices such as mobile phones, laptops, camcorders, and digital cameras has become commonplace, the development of technologies related to such mobile devices is becoming active. Furthermore, rechargeable secondary batteries are being utilized as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (P-HEVs) as a solution to address air pollution caused by conventional gasoline vehicles using fossil fuels; consequently, the need for the development of secondary batteries is increasing.

[0005] Currently commercialized rechargeable batteries include nickel-cadmium, nickel-hydrogen, nickel-zinc, and lithium-ion batteries. Among these, lithium-ion batteries are gaining attention for their advantages, such as the ability to freely charge and discharge with almost no memory effect compared to nickel-based batteries, a very low self-discharge rate, and high energy density.

[0006] The manufacturing process of such lithium secondary batteries is broadly divided into three stages: electrode process, assembly process, and formation process. The electrode process is further divided into active material mixing process, electrode coating process, rolling process, slitting process, and winding process. Among these, the rolling process is a process of compressing an electrode substrate to a desired thickness by passing it between a pair of high-temperature heated rolling rolls in order to reduce the thickness of the electrode substrate after the coating process to increase capacity density and increase adhesion between the electrode current collector and the electrode active material layer.

[0007] Meanwhile, as the need for high-capacity and high-performance secondary batteries increases, the electrode loading amount is gradually increasing, but the impregnation of the electrolyte is actually decreasing, so effective measures to improve electrolyte impregnation are required.

[0008] The present invention relates to a method for manufacturing an electrode, and aims to improve the electrolyte impregnation of the electrode and enhance the performance of the battery by applying and drying an electrode active material slurry containing an electrode active material having an average particle size (D50) of 4 μm or less, and then rolling it using a rolling roll having a surface roughness Ry value of 1 μm or more.

[0009] One embodiment of the present invention provides a method for manufacturing an electrode comprising the steps of: applying an electrode active material slurry to one or both sides of an electrode current collector; drying the electrode active material slurry to form an electrode active material layer; and rolling the electrode active material layer, wherein the electrode active material slurry comprises an electrode active material having an average particle size (D50) of 4 μm or less, and the rolling is performed using a rolling roll having a surface roughness Ry value of 1 μm or more.

[0010] In addition, another embodiment of the present invention provides an electrode comprising an electrode current collector and an electrode active material layer formed on one or both sides of the electrode current collector, wherein the electrode active material layer comprises an electrode active material having an average particle size (D50) of 4 μm or less, and the surface roughness Ry value of the electrode active material layer is 0.8 μm or more.

[0011] In addition, one embodiment of the present invention provides a secondary battery comprising the electrode.

[0012] In the method for manufacturing an electrode according to the present invention, an electrode active material slurry containing an electrode active material having an average particle size (D50) of 4 μm or less is coated and dried, and then rolled with a rolling roll having a surface roughness Ry value of 1 μm or more to manufacture an electrode having an appropriate surface roughness Ry value. Accordingly, electrolyte impregnation is improved, and a high-performance secondary battery can be realized.

[0013] FIG. 1 is a schematic diagram showing a rolling process according to one embodiment of the present invention.

[0014] FIG. 2 is a schematic diagram showing a rolling roll used in a rolling process according to one embodiment of the present invention.

[0015] Figure 3 is a figure showing the change in surface roughness Ry value of a rolling roll depending on the presence or absence of a DLC coating layer.

[0016] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0017] To clearly explain the present invention, parts unrelated to the description have been omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0018] Furthermore, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, and the present invention is not necessarily limited to what is illustrated. Thicknesses have been enlarged in the drawings to clearly represent various layers and regions. Additionally, for convenience of explanation, the thickness of some layers and regions has been exaggerated in the drawings.

[0019] Furthermore, when describing a part such as a layer, membrane, region, or plate as being "on," "on top of," or "on" another part, this should be interpreted to include not only cases where the corresponding part is "immediately above" another part, but also cases where there is another part in between. Conversely, when describing a corresponding part such as a layer, membrane, region, or plate as being "immediately above" another part, it may mean that there is no other part in between.

[0020] Furthermore, stating that something is "above" or "on" a reference part means being located above or below the reference part, and does not necessarily imply being located "above" or "on" in the opposite direction of gravity. On the other hand, just as describing another part as being "above" or "on" can be understood by referring to the aforementioned content, describing another part as being "below," "under," or "in" can also be understood.

[0021] Furthermore, throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0022] In this specification, “primary particle” means a particle formed by the aggregation of one to several tens of crystal grains.

[0023] In this specification, “secondary particle” refers to a particle formed by the aggregation of tens to hundreds of multiple primary particles. More specifically, the secondary particle is an aggregate of 40 or more primary particles.

[0024] In this specification, "average particle size (D50)" refers to the particle size at 50% of the volume cumulative particle size distribution of the positive electrode active material. The average particle size (D50) can be measured using a laser diffraction method. For example, after dispersing the positive electrode active material powder in a dispersion medium, it can be measured by introducing it into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating it with ultrasound of about 28 kHz at an output of 60 W, obtaining a volume cumulative particle size distribution graph, and then determining the particle size corresponding to 50% of the volume cumulative amount.

[0025] In this specification, surface roughness Ry refers to the maximum height roughness value representing the height difference between the highest and lowest points of the sample surface within the measurement interval, and Ra refers to the arithmetic mean roughness value represented by the arithmetic mean of the height deviations of the sample surface within the same measurement interval.

[0026] In this specification, a contact measuring instrument or a laser measuring instrument may be used to measure surface roughness. Specifically, since the surface roughness of a rolling roll is often measured while mounted on the equipment and surface sampling is difficult, it is preferable to use a contact measuring instrument (e.g., Mitutoyo SJ-210). On the other hand, in the case of an electrode, since the surface is relatively soft, it is preferable to use a non-contact measuring instrument such as a laser measuring instrument (e.g., Keyence VK-X3000).

[0027]

[0028] Hereinafter, a method for manufacturing an electrode according to one embodiment of the present invention will be described.

[0029] A method for manufacturing an electrode according to one embodiment of the present invention comprises the steps of: applying an electrode active material slurry to one or both sides of an electrode current collector; drying the electrode active material slurry to form an active material layer; and rolling the electrode active material layer.

[0030] The above electrode active material slurry contains an electrode active material having an average particle size (D50) of 4 μm or less, and the rolling is performed using a rolling roll having a surface roughness Ry value of 1 μm or more.

[0031] In conventional electrode manufacturing processes, rolling rolls with a surface roughness Ry of 0.4 μm or less have been used, and the surface roughness of the electrode after rolling was not recognized as an important factor determining the performance of the battery. However, after continuous research, the inventors of this application confirmed that the electrode surface roughness values ​​Ry and Ra after rolling not only affect the impregnation of the electrolyte but are also factors closely related to the capacity and performance of the battery. Furthermore, it was confirmed that the average particle size (D50) of the electrode active material included in the electrode active material layer and the surface roughness Ry of the rolling roll used in the rolling process have a very significant influence on the surface roughness (Ry, Ra) of the manufactured electrode.

[0032] Therefore, the present invention can provide a battery with excellent performance while improving the impregnation of the electrolyte by optimizing the average particle size (D50) of the electrode active material and the surface roughness (Ry) value of the rolling roll.

[0033] FIG. 1 schematically illustrates a rolling process according to one embodiment of the present invention.

[0034] Referring to FIG. 1, the rolling step according to the present invention involves transporting a pre-electrode including an electrode active material layer (22) formed by applying and drying an electrode active material slurry on one surface of an electrode current collector (21) through a transport roller (not shown), and manufacturing an electrode (20) by rolling the transported pre-electrode using a pair of rolling rolls (10A, 10B) located at the top and bottom facing each other.

[0035] Here, the pre-electrode refers to the state before rolling is performed on the electrode. That is, it refers to an electrode in a dried state after applying an electrode active material slurry onto an electrode current collector.

[0036] Meanwhile, the electrode current collector (21) may be a positive current collector or a negative current collector.

[0037] Specifically, the positive current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery; for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive current collector may also have fine irregularities formed on its surface to increase adhesion with the positive active material layer, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible. In addition, the positive current collector may typically have a thickness of 3 to 500 μm.

[0038] In addition, specifically, the negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the negative current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to strengthen the bonding force with the negative active material layer. Such a negative current collector may be formed in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0039] The above electrode active material slurry refers to a mixture of an electrode active material, optionally a binder, a conductive material, a filler, a dispersant, etc., in a solvent.

[0040] At this time, the electrode active material may be a positive electrode active material or a negative electrode active material.

[0041] The above-mentioned cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and various combinations are possible, for example, lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt oxide (e.g., LiCoO2, etc.), lithium-nickel oxide (e.g., LiNiO2, etc.), lithium-nickel-manganese oxide (e.g., LiNi 1-Y0 Mn Y0 O2(here, 0 <Y0<1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O2(where, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2), etc.), or lithium-nickel-cobalt-manganese-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2)O2(wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of independent elements, respectively, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, p2 + q2 + r2 + s2 = 1), etc.), lithium iron phosphate (e.g., Li 1+a1 Fe 1-x1 M x1 (PO 4-b1 )X b1 (Here, M is one or more selected from Al, Mg and Ti, and X is one or more selected from F, S and N, and -0.5≤a1≤0.5, 0≤x1≤0.5, 0≤b1≤0.1) etc., and any one or more of these compounds may be included.

[0042] The above-mentioned cathode active material is one or more carbon-based materials selected from the group consisting of graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, Ketjen black, Super P, graphene, and fibrous carbon, Si-based materials, Li x0 Fe2O3(0≤x0≤1), Li x0 WO2(0≤x0≤1), Sn x0 Me 1-x0 Me y0 O z0(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x0≤1; 1≤y0≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; Al, Cu, Ge, Si, Sn 등의 금속; 리튬 합금; 규소계 합금; 주석계 합금; SiO, SiO2, SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물; 리튬 티타늄 산화물 등을 포함할 수 있고, 상세하게는 음극 활물질로서, 상기 흑연을 포함할 수 있다.

[0043] In one embodiment, the average particle size (D50) of the electrode active material may be 4 μm or less, specifically 0.5 μm to 4 μm, and more specifically 1 μm to 3.5 μm. If the average particle size (D50) of the electrode active material exceeds 4 μm, the surface roughness (Ry, Ra) value of the electrode cannot be increased to a desired level even if rolled with a rolling roll having a surface roughness Ry value of 1 μm or more.

[0044] Specific examples of other components of the electrode active material slurry will be described later.

[0045] In one embodiment, the surface roughness Ry value of the rolling roll may be 1 μm or more, or 1 μm to 15 μm, or 1 μm to 13 μm, or 2 μm to 13 μm. If the surface roughness Ry value of the rolling roll used in the electrode rolling process is less than 1 μm, the surface roughness Ry and Ra values ​​of the rolled electrode cannot be increased to a desired level, and if the surface roughness Ry value of the rolling roll exceeds 15 μm, damage may occur to the electrode after rolling.

[0046] FIG. 2 is a schematic diagram showing a rolling roll used in a rolling process according to one embodiment of the present invention.

[0047] Referring to FIGS. 1 and 2 to describe a rolling roll according to one embodiment of the present invention more specifically, the rolling rolls (10A, 10B) each include a base material (13a, 13b); a plating layer (11a, 11b) formed on the surface of the base material (13a, 13b); and a DLC (Diamond-Like-Carbon) coating layer (12a, 12b) formed on the opposite side of the plating layer (11a, 11b) facing the base material (13a, 13b).

[0048] Here, the base material (13a, 13b) may be formed into a cylindrical shape using materials such as alloy steel, high-carbon chromium steel, etc., but is not limited thereto.

[0049] In addition, the Vickers hardness of the plating layers (11a, 11b) is 1,000 HV, specifically 1,000 HV to 3,000 HV, and even more specifically 1,000 HV to 2,500 HV. As the Vickers hardness of the plating layers (11a, 11b) satisfies the above range, the surface roughness Ry value of the rolling rolls (10A, 10B) can be maintained constant even when a repetitive rolling process is performed.

[0050] The Vickers hardness mentioned above is measured by a standard method for measuring the hardness of a material, and is a value calculated from the surface area of ​​the mark engraved by a pyramidal diamond indenter and the applied load.

[0051] Meanwhile, if the Vickers hardness of the plating layer (11a, 11b) is less than 1,000 HV, the surface of the rolling roll (10A, 10B) may wear down as the rolling process progresses, and the surface roughness (Ry) may decrease. If the Vickers hardness exceeds 3,000 HV, there is a risk of deformation and / or cracking due to the repetitive rolling process.

[0052] The material of the plating layer (11a, 11b) is not limited as long as it is a material that satisfies Vickers hardness, but specifically may include high-hardness hard chromium (HCr) or tungsten carbide (WC). The high-hardness hard chromium may be manufactured by adding an additive, such as a carbon-containing additive, to general hard chromium that exhibits about 800 HV to 900 HV.

[0053] At this time, the thickness (t1) of the plating layer (11a, 11b) is 10㎛ to 500㎛, more specifically 10㎛ to 400㎛, and even more specifically 30㎛ to 200㎛. If the thickness (t1) of the plating layer is formed to be thicker than the above range, the amount of hydrogen gas or hydrogen ions generated inside the plating layer (11a, 11b) increases, and the phenomenon of detachment of the DLC coating layer (12a, 12b) may be accelerated.

[0054] By forming a DLC coating layer (12a, 12b) on the plating layer (11a, 11b), wear caused by rolling friction can be prevented, thereby maintaining the surface roughness (Ry) of the rolling roll (10A, 10B).

[0055] In this way, an experiment was conducted to verify the change in the surface roughness (Ry) value of the rolling roll depending on whether or not the DLC coating layer (12a, 12b) is formed.

[0056] Specifically, a rolling roll with a surface roughness (Ry) of 2 μm (base material / WC / DLC coating layer) manufactured in Example 2 to be described later, a rolling roll with a tungsten carbide (WC) plating layer (thickness 150 μm, Vickers hardness 1400 HV, surface roughness (Ry) 0.2 μm) formed on the base material, and a rolling roll with a hard chromium (HCr) plating layer (thickness 150 μm, Vickers hardness 850 HV, surface roughness (Ry) 0.3 μm) formed on the base material were mounted on a rolling device under the same conditions and a rolling test was performed. Subsequently, the change in surface roughness (Ry) according to the number of days of use was measured and the results are shown in FIG. 3.

[0057] Referring to FIG. 3, the rolling roll manufactured in Example 2 maintained a constant surface roughness (Ry) even after more than 160 days of use, whereas the rolling rolls without a DLC coating layer were found to have a very large range of change in surface roughness (Ry) or a short period of use.

[0058] Here, the DLC coating layer (12a, 12b) may include a buffer layer (not shown) formed on a surface facing the plating layer (11a, 11b) and a DLC layer (not shown) formed on a surface opposite to the surface facing the plating layer (11a, 11b) of the buffer layer.

[0059] The above buffer layer is intended to increase the bonding strength between the plating layer (11a, 11b) and the DLC layer, and can be formed using a material that has high affinity with the material of the plating layer (11a, 11b) and the DLC layer, such as CrN, CrC, etc.

[0060] The thickness of the above buffer layer can be formed to be 0.1㎛ to 1㎛, more specifically 0.3㎛ to 0.8㎛, and even more specifically 0.4㎛ to 0.7㎛.

[0061] The above DLC layer may be formed by coating on the buffer layer using one or more methods selected from the group consisting of, for example, PECVD (plasma enhanced chemical vapor deposition), ion plating, laser ablation, and filtered vacuum arc plasma coating.

[0062] The thickness of the above DLC layer can be formed to be 0.5㎛ to 3.5㎛, specifically 0.1㎛ to 3.0㎛.

[0063] In one embodiment, the thickness of the DLC coating layer (12a, 12b) is 1 μm to 4.5 μm, more specifically 1 μm to 4 μm, and even more specifically 1.5 μm to 3.5 μm. Since the DLC coating layer (12a, 12b) has a high Vickers hardness of its own, if it is formed too thick, brittleness increases, and if it is formed too thin, the DLC coating layer (12a, 12b) may detach.

[0064] In another embodiment, the Vickers hardness of the rolling rolls (10A, 10B) themselves may be 1,500 HV or higher, more specifically 1,500 HV to 3,500 HV, and more specifically 1,500 HV to 3,000 HV.

[0065]

[0066] Next, an electrode according to one embodiment of the present invention will be described.

[0067] Referring again to FIG. 1, an electrode (20) according to one embodiment of the present invention comprises an electrode current collector (21) and an electrode active material layer (22) formed on one or both sides of the electrode current collector (21), wherein the electrode active material layer (22) comprises an electrode active material having an average particle size (D50) of 4 μm or less, and the surface roughness Ry value of the electrode active material layer is 0.8 μm or more.

[0068] In this way, the surface roughness Ry value of the electrode active material layer may be 0.8 μm or more, specifically 0.8 μm to 10 μm. More specifically, when the electrode active material layer is a positive electrode active material layer, the surface roughness Ry value may be 1.3 μm to 8 μm, and when it is a negative electrode active material layer, the surface roughness Ry value may be 0.8 μm to 6 μm. When the surface roughness Ry of the electrode active material layer satisfies the above range, an excellent electrolyte absorption rate can be exhibited.

[0069] In one embodiment, when the electrode (20) is a negative electrode, the surface roughness Ra value of the negative electrode active material layer may be 0.1 μm or more, specifically 0.1 μm to 10 μm, and more specifically 0.1 μm to 8 μm.

[0070] Meanwhile, when the electrode (20) is a positive electrode, the surface roughness Ra value of the positive electrode active material layer may be 0.15㎛ or more, specifically 0.15㎛ to 10㎛, and more specifically 0.15㎛ to 8㎛.

[0071] When the electrode (20) of the present invention satisfies both of the aforementioned surface roughness values ​​Ra and Ry, the electrolyte impregnation can be effectively improved due to the increase in the surface area of ​​the electrode (20). In addition, problems such as damage to the separator and increased resistance that may occur due to an excessive increase in the surface roughness of the electrode (20) can be prevented.

[0072]

[0073] Finally, a secondary battery according to one embodiment of the present invention will be described.

[0074] The above secondary battery includes the aforementioned electrode (20). At this time, the electrode (20) may be a positive electrode or a negative electrode.

[0075] Specifically, the secondary battery may be in the form of an electrode assembly formed by interposing a positive electrode, a negative electrode, and a separator between the positive and negative electrodes, inserted into a case or pouch, and an electrolyte injected to impregnate the electrode assembly with the electrolyte.

[0076] The above-mentioned positive electrode may have a structure in which a positive active material layer is formed on one or both sides of a positive current collector. The above-mentioned positive active material layer comprises a positive active material, and in addition to the positive active material, a binder, conductive material, filler, dispersant, etc. may be optionally further included as needed.

[0077] The above-mentioned types of positive current collectors, positive active materials, and average particle size (D50) are as described above.

[0078] The above positive active material may be included in an amount of 60 to 99 weight%, or 70 to 99 weight%, or 80 to 98 weight% based on the total weight of the positive active material layer.

[0079] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1% to 10% by weight based on the total weight of the positive active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0080] The above conductive material is a component for further improving the conductivity of the positive electrode active material and may be included in an amount of 1% to 30% by weight, 1% to 20% by weight, or 1% to 10% by weight based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0081] In addition, a filler may be optionally added to the anode as a component that inhibits expansion. Such a filler is not particularly limited as long as it can inhibit the expansion of the electrode without causing chemical changes in the battery, and for example, olifin-based polymers such as polyethylene and polypropylene; fibrous materials such as glass fibers and carbon fibers; etc. may be used.

[0082] In addition, a dispersant may be optionally added to the anode. Specifically, the dispersant may be N-methylpyrrolidone, polyvinylpyrrolidone, etc., and may be included in an amount of 0% to 0.5% by weight or 0.05% to 0.4% by weight based on the total weight of the anode active material layer.

[0083] The above-mentioned cathode may have a structure in which a cathode active material layer is formed on one or both sides of a cathode current collector. The cathode active material layer comprises a cathode active material, and in addition to the cathode active material, a binder, conductive material, filler, dispersant, etc. may be optionally further included as needed.

[0084] The type of the negative current collector, the type of negative active material, and the average particle size (D50) are as described above.

[0085] The above negative electrode active material layer includes a positive electrode active material, and the negative electrode active material may be included in an amount of 80% to 99% by weight, 82% to 99% by weight, or 84% to 99% by weight based on the total weight of the negative electrode active material layer.

[0086] The binder, conductive material, filler, and dispersant included in the above-mentioned cathode active material layer may be subject to the description of the anode described above.

[0087] The above separator may be used without limitation as long as it is commonly used as a separator in a secondary battery. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0088] Alternatively, the above-mentioned separator may be an SRS separator having a structure in which an organic-inorganic mixed layer containing inorganic particles and a binder is formed on one or both sides of a polymer substrate.

[0089] The above electrolyte may include an organic solvent and an electrolyte.

[0090] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0091] Examples of electrolytes that can be used when manufacturing secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., but are not limited to these.

[0092] Specifically, the above electrolyte may include a lithium salt.

[0093] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, as the anion of the above lithium salt, F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt is, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2,LiCl, LiI, or LiB(C2O4)2, etc., may be used. It is preferable to use the lithium salt within a concentration range of 0.1M to 4.0M, preferably 0.5M to 3.0M, and more preferably 1.0M to 2.0M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0094] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 10 weight% based on the total weight of the electrolyte.

[0095] Except for including the electrode of the present invention, the above secondary battery can be manufactured according to a general secondary battery manufacturing method with the configuration of a general secondary battery.

[0096]

[0097] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

[0098]

[0099] [Experimental Example]

[0100] Experimental Example 1.

[0101] Example 1.

[0102] A cylindrical base material made of high-carbon chrome steel with a diameter of 750 mm was coated with tungsten carbide (WC) to a thickness of 150 μm and then polished to form a plating layer with a surface roughness (Ry) of 1 μm and a Vickers hardness of 1400 HV. Subsequently, CrN was coated to a thickness of 0.5 μm on the surface of the plating layer, and additionally DLC was coated to a thickness of 2 μm to form a DLC coating layer with a total thickness of 2.5 μm, thereby manufacturing a rolling roll with a surface roughness (Ry) of 1 μm.

[0103] A cathode slurry containing a cathode active material (artificial graphite) with an average particle size (D50) of 1 μm, a conductive material (acetylene black), and a binder (PVDF) in a weight ratio of 96.7:0.3:3 was applied to a copper (Cu) thin film and dried to produce a pre-rolling cathode. Subsequently, the pre-rolling cathode was rolled using the aforementioned pair of rolling rolls under a linear pressure of 0.88 ton / cm.

[0104]

[0105] Example 2.

[0106] A rolling roll (rolling roll surface roughness: 2㎛) was manufactured in the same manner as in Example 1, except that the surface roughness of the plating layer was formed to 2㎛ in Example 1, and a pre-rolling cathode identical to that in Example 1 was rolled using the manufactured rolling roll.

[0107]

[0108] Comparative Example 1.

[0109] A rolling roll (rolling roll surface roughness: 0.3 μm) was manufactured in the same manner as in Example 1, except that the surface roughness of the plating layer was formed to 0.3 μm in Example 1, and a pre-rolling cathode identical to that in Example 1 was rolled using the manufactured rolling roll.

[0110]

[0111] Using a laser measuring instrument (Keyence VK-X3000), the surface roughness values ​​Ra and Ry of the rolled cathodes in Example 1, Example 2 and Comparative Example 1 were measured and are shown in Table 1 below.

[0112] Comparative Example 1 Example 1 Example 2 Rolled Roll Surface Roughness (Ry, μm) 0.3 1.0 2.0 Electrode Surface Roughness Ra (μm) 0.0 9 0.1 1 0.2 3 Ry (μm) 0.6 9 0.8 8 1.5 9

[0113]

[0114] After dropping 1 μl of PC (propylene carbonate) solution onto the rolled cathode surface in Example 1, Example 2 and Comparative Example 1, the time until the PC solution was completely absorbed into the cathode was measured, and the results are shown in Table 2 below.

[0115] Comparative Example 1 Example 1 Example 2 Impregnation time (sec) 170 154 142

[0116]

[0117] From the results of Tables 1 and 2 above, it was confirmed that Examples 1 and 2, rolled using a rolling roll with a surface roughness (Ry) of 1 μm or 2 μm, had an increased surface roughness (Ry, Ra value) of the cathode compared to Comparative Example 1, rolled using a rolling roll with a surface roughness (Ry) of 0.3 μm, and also had excellent electrolyte impregnation properties.

[0118]

[0119] Experimental Example 2.

[0120] Comparative Example 2.

[0121] A pre-rolling cathode prepared by applying and drying a cathode slurry containing a cathode active material containing artificial graphite (D50: 16.5㎛) and natural graphite (D50: 17.5㎛) in a weight ratio of 1:1, a conductive material (Super-C65), and a binder (mixture of acrylic binder and PVDF binder) in a weight ratio of 96.85: 0.5: 1.6: 1.05 onto a copper (Cu) thin film, was rolled using a pair of rolling rolls (surface roughness Ry: 0.3㎛) prepared in Comparative Example 1 under a linear pressure of 1.08 ton / cm.

[0122]

[0123] Comparative Example 3.

[0124] The same pre-rolling cathode as in Comparative Example 2 was rolled using a pair of rolling rolls (surface roughness Ry: 1 ​​μm) manufactured in Example 1.

[0125]

[0126] Comparative Example 4.

[0127] The same pre-rolling cathode as in Comparative Example 2 was rolled using a pair of rolling rolls (surface roughness Ry: 2㎛) manufactured in Example 2.

[0128]

[0129] The surface roughness (Ra, Ry) and impregnation time of the PC solution of Comparative Examples 2 to 4 were measured using the same method as in Experimental Example 1, and the results are shown in Table 3 below.

[0130] Comparative Example 2 Comparative Example 3 Comparative Example 4 Rolling Roll Surface Roughness (Ry, μm) 0.3 1.0 2.0 Electrode Surface Roughness Ra (μm) 0.8 7 0.8 4 0.8 4 Ry (μm) 5.5 9 6.1 2 6.0 0 Impregnation Time (sec) 26 28 27

[0131]

[0132] Referring to Table 3 above, in the case of a cathode containing an active material with a large average particle size (D50), even if the surface roughness (Ry) of the rolling roll is increased from 0.3㎛ to 1㎛ and 2㎛, the surface roughness Ry of the cathode increases only slightly, while Ra actually decreases, and accordingly, it can be confirmed that the electrolyte impregnation is also reduced.

[0133]

[0134] Experimental Example 3.

[0135] Example 3.

[0136] The anode, prepared by applying and drying an anode slurry containing an anode active material (lithium-nickel-manganese-cobalt oxide) with an average particle size (D50) of 3.6 μm, a conductive material (carbon nanotube), a binder (PVDF), and a dispersant in a weight ratio of 97.21 : 1.2 : 1.23 : 0.36 onto an aluminum (Al) thin film, was rolled using a pair of rolling rolls (surface roughness Ry: 1 ​​μm) prepared in Example 1 under a linear pressure of 3.78 ton / cm.

[0137]

[0138] Example 4.

[0139] The anode identical to that in Example 3 above was rolled using a pair of rolling rolls (surface roughness Ry: 2㎛) manufactured in Example 2.

[0140]

[0141] Comparative Example 5.

[0142] The anode identical to Example 3 above was rolled using a pair of rolling rolls (surface roughness Ry: 0.3 μm) manufactured in Comparative Example 1.

[0143]

[0144] Using a laser measuring instrument (Keyence VK-X3000), the surface roughness values ​​Ra and Ry of the rolled anodes in Example 3, Example 4 and Comparative Example 5 were measured and are shown in Table 4 below.

[0145] Comparative Example 5 Example 3 Example 4 Rolled Roll Surface Roughness (Ry, μm) 0.3 1.0 2.0 Electrode Surface Roughness Ra (μm) 0.1 4 0.1 6 0.2 6 Ry (μm) 1.2 3 1.3 6 1.9 3

[0146]

[0147] In Examples 3, 4, and Comparative Example 5, 1 μl of PC (propylene carbonate) solution was dropped onto the rolled anode surface, and the time until the PC solution was completely absorbed into the anode was measured, and the results are shown in Table 5 below.

[0148] Comparative Example 5 Example 3 Example 4 Impregnation time (sec) 622517590

[0149]

[0150] From the results of Tables 4 and 5 above, it can be confirmed that the examples rolled using rolling rolls with a surface roughness (Ry) of 1 μm or more, not only at the cathode but also at the anode, show increased anode surface roughness (Ry, Ra) compared to the comparative example and exhibit excellent electrolyte impregnation.

[0151]

[0152] Experimental Example 4.

[0153] Comparative Example 6.

[0154] A pre-rolled anode prepared by applying and drying an anode active material containing a lithium transition metal oxide with an average particle size (D50) of 13 μm and a lithium transition metal oxide with an average particle size (D50) of 11 μm in a weight ratio of 1:1, a conductive material (acetylene black), and a binder (PVDF) in a weight ratio of 98.54:0.26:1.2 onto an aluminum (Al) thin film, was rolled using a pair of rolling rolls (surface roughness Ry: 0.3 μm) prepared in Comparative Example 1 under a linear pressure of 1.37 ton / cm.

[0155]

[0156] Comparative Example 7.

[0157] The anode identical to Comparative Example 6 above was rolled using a pair of rolling rolls (surface roughness Ry: 1 ​​μm) manufactured in Example 1 above.

[0158]

[0159] Comparative Example 8.

[0160] The anode identical to Comparative Example 6 above was rolled using a pair of rolling rolls (surface roughness Ry: 2㎛) manufactured in Example 2 above.

[0161]

[0162] The surface roughness (Ra, Ry) and impregnation time of the PC solution of Comparative Examples 6 to 8 were measured using the same method as in Experimental Example 1, and the results are shown in Table 6 below.

[0163] Comparative Example 6 Comparative Example 7 Comparative Example 8 Rolled Roll Surface Roughness (Ry, μm) 0.3 1.0 2.0 Electrode Surface Roughness Ra (μm) 0.4 7 0.4 3 0.4 4 Ry (μm) 3.7 6 3.5 2 3.7 6 Impregnation Time (sec) 4 1 4 5 3 2 4 8 4

[0164]

[0165] Referring to Table 6 above, it can be seen that in the rolling process of an anode containing an active material with a large average particle size (D50), even if the surface roughness (Ry) of the rolling roll is increased from 0.3㎛ to 1㎛ and 2㎛, the surface roughness (Ry, Ra) of the anode actually decreases, and accordingly, the electrolyte impregnation ability also decreases.

[0166]

[0167] Through Experimental Examples 1 to 4, it was confirmed that by rolling an electrode active material layer containing an electrode active material satisfying the average particle size (D50) defined in the present invention with a rolling roll having a surface roughness (Ry) of 1 μm or more, the surface roughness (Ry, Ra) of the manufactured electrode can be increased, and the electrolyte impregnation performance is improved due to the resulting increase in surface area.

[0168] [Explanation of the symbol]

[0169] 10A, 10B: Rolled rolls

[0170] 11a, 11b: Plating layer

[0171] 12a, 12b: DLC coating layer

[0172] 13a, 13b: Base material

[0173] 20: Electrode

[0174] 21: Electrode current collector

[0175] 22: Electrode active material layer

Claims

1. A step of applying an electrode active material slurry to one or both sides of an electrode current collector; A step of drying the electrode active material slurry to form an electrode active material layer; and The above electrode active material layer includes the step of rolling, The above electrode active material slurry includes an electrode active material having an average particle size (D50) of 4㎛ or less, and The above rolling is a method for manufacturing an electrode, performed using a rolling roll having a surface roughness Ry value of 1 μm or more.

2. In Paragraph 1, A method for manufacturing an electrode in which the average particle size (D50) of the above electrode active material is 0.5㎛ to 4㎛.

3. In Paragraph 1, A method for manufacturing an electrode in which the surface roughness Ry value of the above-mentioned rolling roll is 1㎛ to 15㎛.

4. In Paragraph 1, A method for manufacturing an electrode comprising: a rolling roll comprising a base material; a plating layer formed on the surface of the base material; and a DLC (Diamond-Like-Carbon) coating layer formed on the opposite side of the plating layer facing the base material.

5. In Paragraph 4, A method for manufacturing an electrode in which the Vickers hardness of the plating layer is 1,000 HV or higher.

6. In Paragraph 4, A method for manufacturing an electrode in which the plating layer comprises high-hardness hard chromium (HCr) or tungsten carbide (WC).

7. In Paragraph 4, A method for manufacturing an electrode in which the thickness of the above DLC coating layer is 1 μm to 4.5 μm.

8. In Paragraph 4, A method for manufacturing an electrode comprising: a buffer layer formed on a surface facing the plating layer and a DLC layer formed on a surface opposite to the surface of the buffer layer facing the plating layer.

9. In Paragraph 1, A method for manufacturing an electrode in which the Vickers hardness of the above-mentioned rolling roll is 1,500 HV or higher.

10. Includes an electrode current collector and an electrode active material layer formed on one or both sides of the electrode current collector, and The above electrode active material layer comprises an electrode active material having an average particle size (D50) of 4㎛ or less, and An electrode having a surface roughness Ry value of 0.8㎛ or more of the above electrode active material layer.

11. In Paragraph 10, The above electrode is a negative electrode, and the electrode has a surface roughness Ra value of the negative electrode active material layer of 0.1 μm or more.

12. In Paragraph 10, The above electrode is a positive electrode, and the electrode has a surface roughness Ra value of the positive active material layer of 0.15 μm or more.

13. In Paragraph 10, The electrode has an average particle size (D50) of the above electrode active material of 0.5㎛ to 4㎛.

14. A secondary battery comprising an electrode according to paragraph 10.

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