Electrode sheet rolling method
The electrode sheet rolling method addresses the issue of wire breakage in tandem rolling by applying specific conditions and processes, achieving a substantial reduction in breakage frequency and maintaining electrode integrity.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- LG ENERGY SOLUTION LTD
- Filing Date
- 2025-11-26
- Publication Date
- 2026-06-04
AI Technical Summary
The tandem rolling process in lithium-ion battery manufacturing leads to a significant difference in elongation rate between coated and uncoated parts of the electrode substrate, increasing the risk of wire breakage due to excessive tension on uncoated areas.
A method for electrode sheet rolling that includes specific conditions such as primary rolling ratios of 50% to 70%, outfeed tension of 150N to 300N, induction heating temperatures of 150°C to 300°C, and surface temperatures of 25°C to 90°C for rolling rolls, along with targeted rolling and non-rolling processes to minimize elongation differences and reduce wire breakage.
The method effectively reduces wire breakage frequency by more than 50% while maintaining electrode quality, as demonstrated through experimental results.
Smart Images
Figure KR2025019817_04062026_PF_FP_ABST
Abstract
Description
Electrode sheet rolling method
[0001] Cross-citation with related application(s)
[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0172130 dated November 27, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.
[0003] The present invention relates to an electrode sheet rolling method, and more specifically, to a tandem rolling method in which rolling conditions are set to a specific range.
[0004] In modern society, as the use of portable devices such as mobile phones, laptops, camcorders, and digital cameras, as well as energy storage systems (ESS), has become commonplace, the development of technologies in related fields 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 receiving the most attention due to their advantages of free charging and discharging, 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.
[0007] Among these, the rolling process is a process in which the electrode substrate is passed between a pair of high-temperature heated rolling rolls to compress it to a desired thickness in order to reduce the thickness of the electrode substrate after the coating process to increase capacity density and to increase the adhesion between the electrode current collector and the electrode active material.
[0008] At this time, the above rolling process is divided into single rolling, which performs rolling only once, and tandem rolling, which performs rolling twice; however, recently, as the development of high-capacity batteries is actively progressing, the tandem rolling process is predominant.
[0009] However, in the case of the above tandem rolling, the elongation rate is higher than that of single rolling, and accordingly, the difference in elongation rate between the retained part coated with the active material layer and the uncoated part where the active material layer is not formed increases, which increases the tension burden on the uncoated part and raises the risk of wire breakage.
[0010] Therefore, there is a need to develop rolling process technology capable of improving such single wires.
[0011] The present invention aims to provide an electrode sheet rolling process capable of improving wire breakage caused by rolling.
[0012] However, the problems that the embodiments of the present invention aim to solve are not limited to the problems described above and can be expanded in various ways within the scope of the technical ideas included in the present invention.
[0013] According to one embodiment of the present invention,
[0014] A method for rolling an electrode sheet comprising a retaining portion coated with an electrode active material slurry on one or both sides of a current collector and an uncoated portion not coated with the electrode active material slurry, wherein
[0015] The above electrode sheet is first rolled by a pair of primary rolling rolls, and
[0016] Tandem rolling is performed by rolling the above primary rolled electrode sheet a second time using a pair of secondary rolling rolls, and
[0017] A method for rolling an electrode sheet that satisfies the following condition 1 when performing the above tandem rolling is provided.
[0018] [Condition 1],
[0019] Primary rolling ratio: 50% to 70%
[0020] Specifically, the primary rolling ratio of the above condition 1 may be 60% to 65%.
[0021] In addition, the electrode sheet rolling method may further satisfy the following condition 2 in that the outfeed tension measured after the second rolling.
[0022] [Condition 2]
[0023] Outfeed tension: 150N to 300N
[0024] Specifically, the outfeed tension of condition 2 above may be 160N to 270N.
[0025] Furthermore, the method may further include an induction heating process for heating the current collector before the first rolling, and the induction heating process may satisfy the following condition 3.
[0026] [Condition 3]
[0027] Induction heating temperature: 150℃ to 300℃
[0028] Specifically, the induction heating temperature of condition 3 above may be 200°C to 260°C.
[0029] Furthermore, the surface temperatures of the first rolling roll and the second rolling roll may each be 25°C to 90°C.
[0030] Specifically, the surface temperatures of the first rolling roll and the second rolling roll may each be 70°C to 90°C.
[0031] In addition, the electrode sheet rolling method further includes a first non-rolling process in which only the non-rolling portion is rolled after the first rolling, and a second non-rolling process in which only the non-rolling portion is rolled after the second rolling.
[0032] The pressure of the above first and second unrolled portion rolling can be 1 kPa to 500 kPa, respectively.
[0033] Specifically, the pressure of the first and second non-rolling portions may be 150 kPa to 400 kPa, respectively.
[0034] Furthermore, the feed speed for rolling the electrode sheet may be 1 m / min to 120 m / min.
[0035] FIG. 1 is a schematic diagram of a rolling device used in an electrode sheet rolling process according to one embodiment of the present invention.
[0036] Figure 2 is a graph confirming the frequency of disconnection according to length in an experimental example of the present invention.
[0037] 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.
[0038] To clearly explain the present invention, parts unrelated to the explanation have been omitted, and the same reference numerals are used for identical or similar components throughout the specification.
[0039] Furthermore, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, and thus 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.
[0040] Furthermore, when a part such as a layer, membrane, region, or plate is said to be "on" or "on" another part, this includes not only the case where it is "directly above" the other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. Also, saying that a part is "on" or "on" a reference part means that it is located above or below the reference part, and does not necessarily mean that it is located "on" or "on" facing the opposite direction of gravity.
[0041] 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.
[0042]
[0043] Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0044] FIG. 1 schematically illustrates a device used for rolling an electrode sheet according to one embodiment of the present invention, and below, a method for rolling an electrode sheet will be described in detail using the schematic diagram of the device in FIG. 1.
[0045] Referring to FIG. 1, the electrode sheet (101) is conveyed by conveying rolls (170), is first rolled by a pair of primary rolling rolls (110), and secondarily rolled by a pair of secondary rolling rolls (120).
[0046] A rolling method performed two or more times in this manner is called tandem rolling. As explained above, this tandem rolling causes a large difference in elongation between the retaining part where the active material layer is formed and the unretaining part where the active material layer is not formed, resulting in a high frequency of wire breakage.
[0047] Accordingly, after conducting in-depth research, the inventors of this application developed process parameters capable of significantly reducing the frequency of wire breakage without other defects in the electrode, and have completed the present invention.
[0048] Here, the electrode sheet (101) includes a retaining portion coated with an electrode active material slurry on one or both sides of a current collector, although not shown in detail in the drawing, and an uncoated portion not coated with the electrode active material slurry.
[0049] The above current collector may be determined differently depending on whether it is a positive or negative electrode, but generally, it may have a thickness of 3 to 500 μm. In addition, it is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or a surface treated with carbon, nickel, titanium, silver, etc., on the surface of copper, aluminum, or stainless steel may be used. The current collector may also form fine irregularities on its surface to increase the adhesion of the electrode active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.
[0050] The type of active material in the above electrode active material slurry is determined depending on whether it is a positive electrode or a negative electrode, and when the electrode (101) sheet is a positive electrode, the electrode active material slurry may include a positive electrode active material, a binder, a conductive material, and other additives.
[0051] The above-mentioned cathode active material is, for example, a compound capable of reversible intercalation and deintercalation of lithium, such as a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), or a lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn Y O2(here, 0 <Y<1), LiMn 2-ZNi 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.), lithium-nickel-cobalt-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.), or lithium iron phosphate (e.g., Li 1+a Fe 1-x M x (PO 4-b )X b (Here, M is one or more selected from Al, Mg and Ti, X is one or more selected from F, S and N, and -0.5≤a≤+0.5, 0≤x≤0.5, 0≤b≤0.1) etc. may be further included.
[0052] The above conductive material is a component for further improving the conductivity of the active material, and such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery. For example, carbon powders such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powders such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive nanomaterials such as carbon nanofibers or carbon nanotubes; fluorinated carbon powder; conductive powders such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used. Among these, the above conductive material may include conductive nanomaterials such as carbon nanotubes or carbon nanofibers to further lower the resistance of the secondary battery and further improve output characteristics.
[0053] Typically, the conductive material may be included in an amount of 1 to 20 weight%, or 1 to 15 weight%, or 1 to 10 weight% based on the total weight of the solids included in the electrode active material slurry.
[0054] The above binder is a component that assists in the bonding of the active material and the conductive material, etc., and in the bonding to the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, nitrile-based rubber, styrene-butadiene rubber, or fluororubber, and a mixture or copolymer of two or more selected from these may also be used.
[0055] Typically, the binder may be included in an amount of 1 to 20 weight%, or 1 to 15 weight%, or 1 to 10 weight% based on the total weight of the solids included in the electrode active material slurry.
[0056] In addition, the above-mentioned other additives may further include, for example, fillers as components that inhibit expansion. The above-mentioned 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.
[0057] When the electrode sheet (101) is a negative electrode, the electrode active material slurry may include, in addition to the negative electrode active material, a binder such as the one described in the positive electrode, a conductive material, and other additives.
[0058] The above-mentioned cathode active material comprises 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, and Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SiO, SiO2, SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물; 리튬 티타늄 산화물 등을 포함할 수 있지만, 당업계에 알려진 것이라면 이들만으로 한정되지 않는다.
[0059] The electrode sheet (101) is first rolled under specific conditions by the primary rolling roll (110), that is, the upper primary rolling roll (111) located above the electrode sheet (101) and the lower primary rolling roll (112) located below it.
[0060] At this time, the first rolling ratio performed by the first rolling may satisfy the following condition 1, and in detail, the first rolling ratio may be 55% to 70%, and more specifically, 60% to 65%.
[0061] [Condition 1]
[0062] Primary rolling ratio: 50% to 70%
[0063] Here, the rolling ratio refers to the ratio of the first rolling load to the target rolling load set to 100. For example, when the target rolling load is 3.8 tons and a rolling load of 3.0 tons is applied in the first rolling, the first rolling ratio is approximately 79%.
[0064] This rolling ratio has the greatest effect on the breakage of the electrode sheet (101). If the first rolling is performed with a rolling ratio that is too low outside the above range, the frequency of electrode breakage increases rapidly after the rolling process of the electrode sheet (101) is completed, and if the first rolling is performed with a rolling ratio that is too high, it is similar to the case of single rolling, and issues regarding electrode quality degradation such as electrode swells on high-density electrodes occur, which is undesirable.
[0065] In this way, after the electrode sheet (101) is first rolled at a specific range of rolling ratios, a second rolling is performed to roll the electrode sheet (101) to have a target thickness or density using a second rolling roll (120), that is, an upper second rolling roll (121) located above the electrode sheet (101) and a lower second rolling roll (122) located below it.
[0066] Here, the first rolling and the second rolling are processes of rolling the entire electrode sheet (101) in the width direction, that is, rolling the retaining portion and the unretaining portion of the electrode sheet (101) entirely.
[0067] However, during such rolling, the uncoated portion is not rolled well due to the difference in thickness between the retained portion and the uncoated portion, that is, the difference in thickness according to the thickness of the active material slurry coating.
[0068] Accordingly, the electrode sheet rolling method according to the present invention may further include, although not illustrated in the drawings, a first rolling of the uncoated portion and a second rolling of the uncoated portion after the first rolling, in which only the uncoated portion is rolled, and a second rolling of the uncoated portion after the second rolling, in which only the uncoated portion is rolled, in each of the first rolling and second rolling processes.
[0069] From this, the difference in elongation between the above-mentioned retained portion and the unretained portion can be reduced.
[0070] At this time, the pressure of the first and second non-rolling portions may be 1 kPa to 500 kPa each, and more specifically, 150 kPa to 400 kPa each.
[0071] In addition, the pressure of the second non-rolling layer may be higher than the pressure of the first non-rolling layer.
[0072] If performed outside the above range at too low a pressure, the effect of rolling the uncoated part cannot be obtained, and if performed at too high a pressure, the elongation rate in the uncoated part becomes too large, which is undesirable.
[0073] Meanwhile, after the second rolling is completed, the electrode sheet (101) is transferred to a cooling roll (190) and cooled. The tension applied to the electrode sheet (101) after it is transferred to the cooling roll (190) after the second rolling is completed is named outfeed tension.
[0074] At this time, after the rolling of the electrode sheet (101) is completed, the frequency of wire breakage of the electrode sheet (101) is also affected by the outfeed tension.
[0075] Accordingly, according to the present invention, the outfeed tension of the electrode sheet (101) measured after the second rolling may further satisfy the following condition 2, specifically 160 N to 270 N, and more specifically 170 N to 250 N.
[0076] [Condition 2]
[0077] Outfeed tension: 150N to 300N
[0078] The above outfeed tension refers to the value measured by the load cell (130) of the force applied to the electrode sheet (101) from the transfer roll while being transferred by the transfer roll (170) after secondary rolling.
[0079] It is difficult to maintain the outfeed tension lower than the above range when considering the transfer speed of the electrode sheet (101), and it is not desirable for it to become larger than the above range as the frequency of wire breakage increases.
[0080] Meanwhile, the rolling according to the present invention can also be performed as hot tandem rolling, and thus, heat can be applied to the electrode sheet (101) along with the rolling.
[0081] Here, the surface temperature of the first rolling roll (110) and the second rolling roll (120) that perform the first rolling and the second rolling may each be 25°C to 90°C, more specifically 60°C to 90°C, and even more specifically 70°C to 90°C.
[0082] Here, the surface temperature can be measured by temperature sensing sensors (113, 114, 123, 124) located next to the upper and lower rolling rolls (111, 112, 121, 122) of the first rolling roll (110) and the second rolling roll (120).
[0083] The surface temperature of the first rolling roll (110) and the second rolling roll (120) does not significantly affect the frequency of wire breakage of the electrode sheet (101), but when performed in the above temperature range, especially when performed at 25°C, it means that no separate heat is applied. However, when hot tandem rolling is performed by applying heat to raise the surface temperature of the first rolling roll (110) and the second rolling roll (120), the line pressure is reduced, which is desirable as it has the effect of minimizing the impact on the electrode due to rolling.
[0084] At this time, when performing hot tandem rolling to increase the surface temperature of the first rolling roll (110) and the second rolling roll (120), although not shown in the drawing, a process of preheating the electrode sheet (101) by a preheating roll may be additionally performed immediately before performing each of the first rolling and second rolling processes.
[0085] Here, preheating can be performed such that the surface temperature of the preheating roll is 30°C to 90°C, specifically 40°C to 80°C, in a range equal to or lower than the surface temperature of the first rolling roll (110) and the second rolling roll (120).
[0086] Meanwhile, according to one embodiment of the present invention, a rolling method may further include an induction heating process for heating the current collector before the first rolling.
[0087] This induction heating process refers to a process in which only the current collector portion is heated by an induction heater (140).
[0088] At this time, the induction heating temperature may also affect the occurrence of a breakage of the electrode sheet (101), and specifically, an appropriate induction heating temperature to reduce the frequency of breakage may satisfy the following condition 3, and in detail, may be 200°C to 280°C, and more specifically, 200°C to 260°C.
[0089] [Condition 3]
[0090] Induction heating temperature: 150℃ to 300℃
[0091] The above induction heating temperature may be a value measured by a temperature sensing sensor when the induction heater (140) generates heat.
[0092] If the induction heating temperature is too low outside the above range, there is a problem where elongation of the uncoated portion does not occur, and if it is too high, the tensile strength of the uncoated portion decreases, which may degrade the electrode quality and is therefore undesirable.
[0093] Meanwhile, the electrode sheet (101) is wound like a roll and is provided from the unwinder (150) to perform rolling, and when rolling is completed by passing through the first rolling roll (110), the second rolling roll (120), and the cooling roll (190) by the transfer rolls (170), it is wound again by the rewinder (160).
[0094] Accordingly, the electrode sheet (101) receives tension while being unwound from the unwinder (150) and transferred to the primary rolling roll (110), and the tension received at this time is named the unwinder tension, and can be measured by a load cell (151) near the transfer roll close to the unwinder (150) similar to the outfeed tension.
[0095] The above unwinder tension is not limited, but may be, for example, 140 N to 250 N, and more specifically, 170 N to 230 N.
[0096] Additionally, when the electrode sheet (101) passes through the first rolling roll (110) and is transferred to the second rolling roll (120), it is transferred by the transfer rolls (170) and receives tension, and this tension is named press tension, and can similarly be measured by a load cell (180) near the transfer roll located between them.
[0097] The above press tension is not limited, but may be, for example, 140 N to 250 N, and more specifically, 170 N to 230 N.
[0098] If the above unwinder tension and the above press tension are each outside the above range, the tension is too small, so the electrode sheet (101) cannot be transferred in close contact with the transfer rolls (170), and there is a possibility of slippage, and if it is too large, there is a problem that the possibility of wire breakage increases, which is undesirable.
[0099] Finally, the electrode sheet (101) receives tension even when it is wound again by the rewinder (160) after the rolling is completed, and this tension is named rewinder tension and can be measured by a load cell (161) near the transfer roll just before it is wound by the rewinder (160).
[0100] The above rewinder tension is not limited, but may be, for example, 200 N to 320 N, and more specifically, 250 N to 300 N.
[0101] If the above rewinder tension is outside the above range, the winding may fail if the tension is too small, and if it is too large, it increases the possibility of electrode sheet disconnection, which is undesirable.
[0102] In this way, tension is applied to the electrode sheet (101) in sections, and as described above, appropriate tension must be maintained so that rolling can be performed without deterioration of electrode quality. Here, since the transfer speed of the electrode sheet (101) not only generally affects the tension applied to the electrode sheet (101) but also affects the performance of rolling to satisfy specific conditions, it is desirable to have an appropriate transfer speed.
[0103] Specifically, in the tandem rolling method according to the present invention, the feed speed for rolling the electrode sheet (101) may be, for example, 1 m / min to 120 m / min, and more specifically, 5 m / min to 110 m / min.
[0104]
[0105] In the following, embodiments are disclosed to aid in understanding the present invention, and the difference in the frequency of wire breakage occurrence when the conditions according to the present invention are satisfied versus when they are not is explained through experimental examples. However, the following embodiments are intended to illustrate the present invention and the scope of the present invention is not limited thereto.
[0106]
[0107] <Experimental Example>
[0108] The frequency of wire breakage was checked while varying the tandem rolling conditions as shown in Table 1 below, indicated in Table 1, and illustrated in Fig. 2.
[0109] Classification Example 1 Comparative Example 1 Electrode Design Active Material Composition LiNi 0.865 Mn 0.065 Co 0.06 Al 0.01 O2(allele / monole = 5:5 (wt%))LiNi 0.865 Mn 0.065 Co 0.06Al 0.01 O2 (allole / monole = 5:5 (wt%)) rolled loading 460 mg / 25 cm 2 460mg / 25cm 2 1st Rolling Thickness 127.5 136 2nd Rolling Thickness 125.5 125.5 Rolling Ratio (1st:2nd) 60:40 30:70 Loading Reduction Rate (After Rolling vs. After Coating) 1.38% 1.51% Process Conditions Induction Heating Temperature 250℃ 250℃ 1st Uncoated Press Pressure 300kpa 300kpa 2nd Uncoated Press Pressure 320kpa 320kpa U / W Tension 200N 200NO / F Tension 240N 240NP Press Tension 230N 230NR / W Tension 300N 300N Wire Breakage Frequency [Times / 10km] 2.32 (▼56.9%) 5.38 Wire Breakage Frequency [Times / LOT] 0.56 1.39
[0110] Referring to Table 1 and Figure 2 above, it can be seen that when the rolling ratio is set higher than in the conventional method, the frequency of wire breakage is reduced by more than 50%.
[0111] 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.
[0112] [Explanation of the symbol]
[0113] 100: Electrode sheet rolling device,
[0114] 110: Primary rolling roll,
[0115] 120: Secondary rolling roll,
[0116] 130: Outfeed tension measuring load cell,
[0117] 140: Induction heating device,
[0118] 150: Unwinder,
[0119] 160: Rewinder,
[0120] 170: Transfer roll,
[0121] 180: Press tension measuring load cell,
[0122] 190: Cooling roll.
[0123] According to the present invention, when process conditions in the rolling process of an electrode sheet are adjusted to satisfy specific conditions, the effect of significantly improving rolling defects without degrading electrode quality is achieved.
Claims
1. A method for rolling an electrode sheet comprising a retaining portion coated with an electrode active material slurry on one or both sides of a current collector and an uncoated portion not coated with the electrode active material slurry, wherein The above electrode sheet is first rolled by a pair of primary rolling rolls, and Tandem rolling is performed by secondarily rolling the above first-pressurized electrode sheet again by a pair of second-rolling rolls, and Electrode sheet rolling method satisfying the following condition 1 when performing the above tandem rolling: [Condition 1] Primary rolling ratio: 50% to 70% 2. In Paragraph 1, An electrode sheet rolling method in which the primary rolling ratio of condition 1 above is 60% to 65%.
3. In Paragraph 1, The above electrode sheet rolling method is an electrode sheet rolling method in which the outfeed tension measured after the second rolling further satisfies the following condition 2: [Condition 2] Outfeed tension: 150N to 300N 4. In Paragraph 3, An electrode sheet rolling method in which the outfeed tension of condition 2 above is 170N to 250N.
5. In Paragraph 1, An electrode sheet rolling method further comprising an induction heating process for heating the current collector prior to the first rolling, wherein the induction heating process satisfies the following condition 3: [Condition 3] Induction heating temperature: 150℃ to 300℃ 6. In Paragraph 5, An electrode sheet rolling method in which the induction heating temperature of condition 3 above is 200℃ to 260℃.
7. In Paragraph 1, An electrode sheet rolling method in which the surface temperatures of the first rolling roll and the second rolling roll are each 25℃ to 90℃.
8. In Paragraph 7, An electrode sheet rolling method in which the surface temperatures of the first rolling roll and the second rolling roll are each 70°C to 90°C.
9. In Paragraph 1, The electrode sheet rolling method further includes a first non-rolling process in which only the non-rolling portion is rolled after the first rolling, and a second non-rolling process in which only the non-rolling portion is rolled after the second rolling. An electrode sheet rolling method in which the pressure of the first and second non-rolling portions is 1 kPa to 500 kPa, respectively.
10. In Paragraph 9, An electrode sheet rolling method in which the pressure of the first and second non-rolled portions is 150 kPa to 400 kPa, respectively.
11. In Paragraph 1, An electrode sheet rolling method in which the feed speed for rolling the electrode sheet is 1 m / min to 120 m / min.