Electrode, secondary battery comprising same, and method for manufacturing same

Abstract

Disclosed are an electrode, a secondary battery comprising same, and an energy storage device, the electrode comprising: an electrode current collector; and an electrode layer located on the electrode current collector and containing an active material, a conductive material, and a binder, wherein: the binder contains a fluorine-based polymer and a modified polyolefin; the surface of the electrode has 5 dichroic regions / m2 or fewer; the modified polyolefin contains at least one functional group of a carboxylic acid anhydride-derived functional group and a carboxylic acid-derived functional group; and the breaking strength per unit width of the electrode layer is 0.6 N / cm or more.

Description

Electrode, secondary battery including same, and method for manufacturing same

[0001] The present invention relates to an electrode, a secondary battery including the same, and a method for manufacturing the same, and more particularly, to an electrode having improved appearance characteristics and mechanical properties, a secondary battery including the same, and a method for manufacturing the same.

[0002] This application claims priority to Korean Application No. 10-2023-0197939 and Korean Application No. 10-2023-0197940, filed December 29, 2023, the entire disclosure of which is incorporated herein by reference.

[0003] The rapid increase in fossil fuel use has led to a growing demand for alternative and clean energy sources. As part of this, the most actively researched area is the field of electrochemical power generation and storage. Secondary batteries are a prime example of electrochemical devices that utilize electrochemical energy, and their applications are expanding. Lithium secondary batteries, a representative type of secondary battery, are not only used as an energy source for mobile devices, but are also increasingly being used as a power source for electric and hybrid electric vehicles, replacing gasoline and diesel vehicles, which are major sources of air pollution. Their applications are also expanding to include auxiliary power sources through grid integration.

[0004] The manufacturing process for these lithium secondary batteries is broadly divided into three stages: the electrode manufacturing process, the electrode assembly manufacturing process, and the formation process. The electrode manufacturing process is further divided into the electrode compound mixing process, the electrode coating process, the drying process, the rolling process, the slitting process, and the coiling process.

[0005] Among these, the electrode mixture mixing process is a process of mixing components for forming an electrode active layer in which an actual electrochemical reaction occurs in the electrode. Specifically, it mixes the electrode active material, which is an essential element of the electrode, and other additives such as conductive materials and fillers, a binder for inter-powder bonding and adhesion to a current collector, and a solvent for imparting viscosity and dispersing powder, to manufacture a slurry having fluidity.

[0006] An electrode coating process is performed to apply the slurry onto an electrically conductive current collector, a drying process is performed to remove the solvent contained in the electrode mixture slurry, and additionally, the electrode is rolled to manufacture the electrode to a predetermined thickness.

[0007] Meanwhile, during the drying process, the solvent contained in the electrode mixture may evaporate, causing defects such as pinholes or cracks in the already formed electrode active layer. Furthermore, since the inside and outside of the active layer are not uniformly dried, the difference in solvent evaporation rates may cause powder floating, i.e., powders in areas that dry first may float to form gaps with areas that dry relatively later, which may deteriorate electrode quality.

[0008] Accordingly, to solve the above problem, a drying device capable of controlling the evaporation rate of the solvent while ensuring that the inside and outside of the active layer are dried uniformly is being considered. However, such drying devices are very expensive and require considerable cost and time to operate, which is disadvantageous in terms of manufacturing process.

[0009] Therefore, research on manufacturing dry electrodes that do not use solvents has been actively conducted recently.

[0010] The above dry electrode is generally manufactured by laminating a free-standing film containing an active material, a binder, a conductive material, etc. and manufactured in the form of a film on a current collector.

[0011] The above conventional dry electrode comprises a process of mixing an active material, a carbon material as a conductive material, and a fiberizable binder together using a blender or the like, fiberizing the binder through a high shear mixing process such as jet milling, and then calendering the mixture into a film form to manufacture a free-standing film. Thereafter, the free-standing film manufactured after calendering is laminated onto a current collector.

[0012] Meanwhile, in the conventional dry electrode manufacturing process, a primer-coated current collector is used to secure adhesion during the process of bonding the dry film and current collector, but there was a problem of additional costs being incurred due to this.

[0013] Therefore, there is an urgent need to develop a dry electrode manufacturing technology that can solve these problems.

[0014] The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide an electrode having excellent appearance characteristics and mechanical properties and improved electrode adhesion, a secondary battery including the same, and a method for manufacturing the same.

[0015] In order to solve the problem of the present invention, according to one aspect of the present invention, an electrode of the following embodiment is provided.

[0016] According to the first implementation example,

[0017] An electrode comprising: an electrode current collector; and an electrode layer positioned on the electrode current collector and including an active material, a conductive material, and a binder;

[0018] The above binder comprises a fluorinated polymer and a modified polyolefin,

[0019] The surface of the above electrode is 5 / m 2 It has the following unusual areas:

[0020] The above modified polyolefin contains at least one functional group among a carboxylic anhydride-derived functional group and a carboxylic acid-derived functional group,

[0021] An electrode is provided, characterized in that the breaking strength per unit width of the electrode layer is 0.6 N / cm or more.

[0022] According to the second embodiment, in the first embodiment,

[0023] The surface of the above electrode is 0 to 3 / m 2 It may have the following unusual areas:

[0024] According to the third embodiment, in the first embodiment or the second embodiment,

[0025] The breaking strength per unit width of the electrode layer may be 0.6 N / cm to 3 N / cm.

[0026] According to the fourth embodiment, in any one of the first to third embodiments,

[0027] The above modified polyolefin may be derived from modified polyolefin particles having an average particle diameter of 0.5 mm or less.

[0028] According to the fifth embodiment, in any one of the first to fourth embodiments,

[0029] The content of the modified polyolefin may be 2 to 40 parts by weight based on 100 parts by weight of the binder.

[0030] According to the sixth embodiment, in any one of the first to fifth embodiments,

[0031] The melting point of the above modified polyolefin may be 140°C or lower.

[0032] According to the seventh embodiment, in any one of the first to sixth embodiments,

[0033] The above modified polyolefin may include at least one of modified polyethylene and modified polypropylene.

[0034] According to the eighth embodiment, in any one of the first to seventh embodiments,

[0035] The above olefin comprises at least one of ethylene and propylene,

[0036] At least one functional group among the above carboxylic acid anhydride-derived functional group and carboxylic acid-derived functional group is selected from the group consisting of maleic anhydride, glutaric anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic monoanhydride, pyromellitic dianhydride, 1,8-naphthalenedicarboxylic acid anhydride, 2,3-naphthalenedicarboxylic acid anhydride, 1,4,5,8-naphthalenetetracarboxylic acid monoanhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid monoanhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, maleic acid, glutaric acid, phthalic acid, trimellitic acid, pyromellitic acid, 1,8-naphthalenedicarboxylic acid, It may be derived from 2,3-naphthalenedicarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, or two or more thereof.

[0037] According to the ninth embodiment, in any one of the first to eighth embodiments,

[0038] The above modified polyolefin may be modified polyethylene.

[0039] According to the tenth embodiment, in any one of the first to ninth embodiments,

[0040] The above modified polyolefin may be at least one of polyethylene containing a maleic anhydride-derived functional group and polypropylene containing a maleic anhydride-derived functional group.

[0041] According to the eleventh embodiment, in any one of the first to tenth embodiments,

[0042] The content of at least one functional group among the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group in the above-mentioned modified polyolefin may be 0.5 to 20 mol%.

[0043] According to the 12th embodiment, in any one of the 1st to 11th embodiments,

[0044] The above binder can be fiberized to bind the active material, conductive material, and modified polyolefin.

[0045] According to the 13th embodiment, in any one of the first to twelfth embodiments,

[0046] The above binder may include polytetrafluoroethylene (PTFE).

[0047] According to the 14th embodiment, in any one of the first to 13th embodiments,

[0048] The content of the active material may be 80 to 98 parts by weight, the content of the conductive material may be 0.5 to 10 parts by weight, the content of the fluorinated polymer may be 0.5 to 5 parts by weight, and the content of the modified polyolefin may be 0.02 to 3.3 parts by weight.

[0049] According to the 15th embodiment, in any one of the 1st to 14th embodiments,

[0050] The above electrode current collector may not include a conductive primer layer on at least one surface.

[0051] According to the 16th embodiment, in any one of the first to fifteenth embodiments,

[0052] The above electrode layer may be derived from a film for a dry electrode.

[0053] According to the 17th implementation example,

[0054] A step of preparing a mixture comprising an active material, a conductive material, and a binder, wherein the binder comprises a fluorinated polymer and a modified polyolefin;

[0055] A step of kneading the mixture at a temperature ranging from 70°C to 170°C and under a pressure higher than atmospheric pressure to produce a mixture lump;

[0056] A step of crushing the above mixture lump to obtain a mixed powder for electrode;

[0057] A step of forming an electrode film by injecting the above electrode-use mixed powder between a plurality of rolls and performing a calendaring process; and

[0058] A method for manufacturing an electrode according to any one of the first to sixteenth embodiments is provided, characterized in that it comprises a step of laminating the electrode film on a metal current collector.

[0059] According to the 18th embodiment, in the 17th embodiment,

[0060] The above modified polyolefin may have an average particle diameter of 0.5 mm or less.

[0061] According to the 19th embodiment, in the 17th embodiment or the 18th embodiment,

[0062] The step of kneading and producing a mixture lump can be performed in a kneader under a pressure higher than atmospheric pressure.

[0063] According to the 20th implementation example,

[0064] A secondary battery is provided, comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode is an electrode according to any one of the first to sixteenth embodiments.

[0065] According to the 21st implementation example,

[0066] An energy storage device is provided that includes a secondary battery according to the 20th embodiment as a unit battery.

[0067] According to one embodiment of the present invention, in addition to a fluorinated polymer as a binder in a film for a dry electrode, a modified polyolefin including at least one functional group derived from a carboxylic acid anhydride and a carboxylic acid is further included, the average particle diameter of the introduced modified polyolefin is controlled to be within a predetermined range or less, the melting point of the introduced modified polyolefin is controlled to be within a predetermined range or less, and the mixing temperature in the mixing process during electrode manufacturing is adjusted to correspond to the melting point of the modified polyolefin, thereby sufficiently melting the modified polyolefin in the mixing process to maximize dispersibility in the electrode material, thereby increasing the mechanical strength of the electrode while at the same time having excellent appearance characteristics and securing adhesion to a current collector that is not primer-coated, thereby providing a dry electrode having a simple manufacturing process and excellent adhesion to a current collector.

[0068] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of ​​the present invention together with the contents of the invention described above, and therefore the present invention should not be interpreted as being limited to matters described in such drawings.

[0069] Figures 1a and 1b are schematic diagrams of a manufacturing process of an electrode film for an electrode applied to an electrode assembly according to one embodiment of the present invention.

[0070] Figure 2 is a schematic diagram of an electrode lamination process according to one embodiment of the present invention.

[0071] Figure 3 is a schematic diagram of an electrode calendaring process and a lamination process according to one embodiment of the present invention.

[0072] Figure 4 is a schematic diagram of an electrode calendaring process and a lamination process according to one embodiment of the present invention.

[0073] Figure 5 is a surface photograph of the electrode of Example 1.

[0074] Figure 6 is a surface photograph of the electrode of Comparative Example 1.

[0075] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0076] Terms or 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.

[0077] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0078] Additionally, throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0079]

[0080] According to one aspect of the present invention,

[0081] An electrode comprising: an electrode current collector; and an electrode layer positioned on the electrode current collector and including an active material, a conductive material, and a binder;

[0082] The above binder comprises a fluorinated polymer and a modified polyolefin,

[0083] The surface of the above electrode is 5 / m 2 It has the following unusual areas:

[0084] The above modified polyolefin contains at least one functional group among a carboxylic anhydride-derived functional group and a carboxylic acid-derived functional group,

[0085] An electrode is provided, characterized in that the breaking strength per unit width of the electrode layer is 0.6 N / cm or more.

[0086] According to one embodiment of the present invention, the electrode may be a positive electrode or a negative electrode, and the active material may be a positive electrode active material or a negative electrode active material.

[0087] The positive electrode active material may include, for example, lithium transition metal oxide; lithium metal iron phosphate; lithium nickel-manganese-cobalt oxide; lithium nickel-manganese-cobalt oxide, an oxide in which a portion of the lithium nickel-manganese-cobalt oxide is substituted with another transition metal; or two or more thereof, but is not limited thereto. Specifically, the positive electrode active material may include, for example, layered compounds such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxides represented by O2 (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein M = Fe, Co, Ni, Cu or Zn); lithium metal phosphate LiMPO4 (wherein M = Fe, CO, Ni or Mn); lithium nickel-manganese-cobalt oxide Li 1+x (Ni a Co b Mn c ) 1-xO2(x = 0 ~ 0.03, a = 0.3 ~ 0.95, b = 0.01 ~ 0.35, c = 0.01 ~ 0.5, a+b+c=1); Lithium nickel-manganese-cobalt oxide partially substituted with aluminum (lithium nickel-manganese-cobalt-aluminum oxide) Li a [Ni b Co c Mn d Al e ] 1-f M 1 f O 2 ( Above M 1 is at least one selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P and S, and 0.8≤a≤1.2, 0.5≤b≤0.99, 0 <c<0.5, 0<d<0.5, 0.01≤e≤0.1, 0≤f≤0.1임), 디설파이드 화합물; Fe2(MoO4)3등을 들 수 있지만, 이들만으로 한정되는 것은 아니다. 구체적으로, 상기 리튬 니켈-망간-코발트-알루미늄 산화물은 Li[Ni 0.88 Co 0.07 Mn 0.04 Al 0.01 ]O2) etc.

[0088] In addition, the negative electrode active material includes carbon such as non-graphitizable carbon and graphite carbon; 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, elements of group 1, 2, and 3 of the periodic table, halogens; 0≤x≤1; 1≤y≤3; 1≤z≤8) and other metal composite oxides; lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; silicon-based oxides such as SiO, SiO / C, and SiO2; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials, etc. can be used.

[0089] According to one embodiment of the present invention, the electrode may be a positive electrode, and thus, the active material may be, specifically, a positive electrode active material, and more specifically, may be a lithium transition metal oxide, a lithium nickel-manganese-cobalt oxide, an oxide in which a portion of lithium nickel-manganese-cobalt oxide is substituted with Al or another transition metal, lithium iron phosphate, or the like.

[0090] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; needle- or branch-shaped conductive whiskers such as zinc oxide whiskers, calcium carbonate whiskers, titanium dioxide whiskers, silicon oxide whiskers, silicon carbide whiskers, aluminum borate whiskers, magnesium borate whiskers, potassium titanate whiskers, silicon nitride whiskers, silicon carbide whiskers, and alumina whiskers; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and among these, one type alone or a mixture of two or more types may be used. Specifically, in order to uniformly mix the conductive material and improve conductivity, it may include at least one selected from the group consisting of activated carbon, graphite, carbon black, and carbon nanotubes, and more specifically, it may include activated carbon.

[0091] The above binder includes a fluorinated polymer and a modified polyolefin.

[0092] According to one embodiment of the present invention, the fluorine-based polymer may be a polymer having one or more fluorine groups in the polymer, and specifically, may include polytetrafluoroethylene (PTFE); PVdF (polyvinylidene fluoride), PVdF-HFP (polyvinylidene fluoride-co-hexafluoropropylene), and the like, PVdF-based copolymers, or two or more thereof. In particular, the fluorine-based binder may include polytetrafluoroethylene (PTFE). In addition, the fluorine-based polymer may include polytetrafluoroethylene alone, or may further include one or more PVdF-based copolymers such as PVdF (polyvinylidene fluoride), PVdF-HFP (polyvinylidene fluoride-co-hexafluoropropylene), and the like in addition to polytetrafluoroethylene.

[0093] According to one embodiment of the present invention, in addition to the fluorinated polymer and modified polyolefin, the binder may further include a non-fluorinated polymer. The non-fluorinated polymer may include polyolefin, polyethylene oxide (PEO), and the like.

[0094] The above modified polyolefin contains at least one functional group among a carboxylic anhydride-derived functional group and a carboxylic acid-derived functional group.

[0095] According to one embodiment of the present invention, the modified polyolefin may be a copolymer including an olefin-derived repeating unit and at least one repeating unit among a carboxylic anhydride-derived repeating unit and a carboxylic acid-derived repeating unit, may be a modified polyolefin including at least one functional group among a carboxylic anhydride-derived functional group and a carboxylic acid-derived functional group as a side chain functional group rather than a repeating unit, may be a copolymer including an olefin-derived repeating unit and at least one repeating unit among a carboxylic anhydride-derived repeating unit and a carboxylic acid-derived repeating unit, and may also include at least one functional group among a carboxylic anhydride-derived functional group and a carboxylic acid-derived functional group as a side chain functional group, or may include two or more of these.

[0096] When the modified polyolefin including at least one of the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group is a copolymer including an olefin-derived repeating unit and at least one of the carboxylic anhydride-derived repeating unit and the carboxylic acid-derived repeating unit, the copolymer may be a block copolymer, a random copolymer, or an alternating copolymer in which the olefin-derived repeating unit and at least one of the carboxylic anhydride-derived repeating unit and the carboxylic acid-derived repeating unit are all connected in the main chain. In addition, the modified polyolefin including at least one of the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group may be a graft copolymer including at least one of the carboxylic anhydride-derived repeating unit and the carboxylic acid-derived repeating unit in the side chain of the polyolefin.

[0097] In addition, according to one embodiment of the present invention, when the modified polyolefin including at least one functional group among the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group is a modified polyolefin including such a functional group as a side chain functional group rather than a repeating unit, the modified polyolefin may be a compound in which at least one hydrogen of the polyolefin is substituted with at least one functional group among the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group.

[0098] The above modified polyolefin may include at least one of modified polyethylene and modified polypropylene. The above modified polyolefin may be modified polyethylene.

[0099] According to one embodiment of the present invention, the modified polyolefin is a polymer including the olefin-derived repeating unit, wherein the olefin-derived repeating unit may be derived from an olefin including at least one of ethylene and propylene.

[0100] According to one embodiment of the present invention, the modified polyolefin may further include an olefin elastomer-derived repeating unit, a styrene-derived repeating unit, an unsaturated hydrocarbon-derived repeating unit, or two or more thereof.

[0101] The above olefin elastomer-derived repeating unit may be a repeating unit derived from 1-butene, 1-octene, etc.

[0102] The above styrene-derived repeating unit may be a repeating unit derived from styrene, substituted styrene, etc. The above unsaturated hydrocarbon-derived repeating unit may be a repeating unit derived from 1,2-butadiene, 1,3-butadiene, etc.

[0103] Specifically, the modified polyolefin may be a poly(ethylene)-(1-butene) copolymer, a poly(ethylene)-(1-octene) copolymer, a poly(ethylene)-(1-propylene) copolymer, a poly(ethylene)-(styrene)-(butadiene) copolymer, etc. containing a carboxylic acid anhydride-derived functional group.

[0104] According to one embodiment of the present invention, at least one functional group among the carboxylic acid anhydride-derived functional group and the carboxylic acid-derived functional group is selected from the group consisting of maleic anhydride, glutaric anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic monoanhydride, pyromellitic dianhydride, 1,8-naphthalenedicarboxylic anhydride, 2,3-naphthalenedicarboxylic anhydride, 1,4,5,8-naphthalenetetracarboxylic acid monoanhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid monoanhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, maleic acid, glutaric acid, phthalic acid, trimellitic acid, pyromellitic acid, It may be derived from 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, or two or more thereof.

[0105] The above modified polyolefin may be at least one of polyethylene containing a maleic anhydride-derived functional group and polypropylene containing a maleic anhydride-derived functional group.

[0106] According to one embodiment of the present invention, the content of at least one functional group among the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group in the modified polyolefin may be 0.5 to 20 mol%, or 0.5 to 15 mol%. When the content of at least one functional group among the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group in the modified polyolefin satisfies this range, excellent reactivity of at least one functional group among the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group may be provided, so that the hydrophilicity of the modified polyolefin is secured, and the electrode layer including such modified polyolefin may have significantly improved adhesive strength at the adhesive surface with a current collector (e.g., a metal current collector).

[0107] At this time, the mol% content of at least one functional group among the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group in the modified polyolefin may be defined as the percentage of the molar number of at least one functional group among the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group (including all cases of repeating units and simple side chain functional groups) to the total molar number of all repeating units and functional groups included in the modified polyolefin (for example, at least one functional group among the olefin-derived repeating unit, the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group (including all cases of repeating units and simple side chain functional groups).

[0108] The electrode according to the present invention adds a modified polyolefin as a binder having high adhesive properties with a current collector in addition to an active material, a conductive material, and a fluorine-based polymer binder to the electrode layer, thereby improving the adhesive strength between the electrode layer and an uncoated current collector without a primer layer at all, without requiring a process of providing a primer layer on the current collector.

[0109] According to one embodiment of the present invention, the electrode layer may include a fiberized binder as a means for binding the active material and the conductive material, and such a fiberized binder has less breakage phenomenon than a conventional non-fiberized binder and has excellent stretchability in the longitudinal direction, thereby improving the flexibility of the electrode layer and the electrode itself including the same. That is, the binder may be fiberized to bind the active material and the conductive material. Specifically, a fluorinated polymer in the binder may be fiberized to bind the active material and the conductive material together with a modified polyolefin, and as a result, may play a role in improving the adhesive strength with the current collector. The fiberization process of the binder will be described in detail in the electrode manufacturing method described below.

[0110] The surface of the electrode of the present invention is 5 / m 2It has the following color region. According to one embodiment of the present invention, the surface of the electrode has 0 to 5 / m 2 , or 0 to 3 / m 2 can have an unusual area.

[0111] Here, the term "colorful region" may mean a region having a color that is different enough to be distinguished from the surrounding normal electrode surface and having a long axis that is longer than a predetermined length.

[0112] Specifically, the above-mentioned heterochromatic region can be defined as a region in which the gray value difference (△GV) of the heterochromatic region (GV of the heterochromatic region) is greater than 20 compared to the gray value (GV) of the surrounding electrode surface surrounding the heterochromatic region (background GV), and the major axis length of the horizontal cross-section of the heterochromatic region parallel to the electrode surface is greater than 1.5 mm.

[0113] The gray value difference (△GV) can be expressed by the following equation.

[0114] Gray value difference (△GV) = |background GV - heterochromatic region GV|

[0115]

[0116] According to one embodiment of the present invention, the gray value difference (△GV) can be measured through an inspection system equipped with a vision camera, an LED light source, and control analysis software. This system analyzes the reflection pattern of light irradiated from a specific direction on the surface of the electrode layer to determine whether a defect exists on the surface, and a surface without defects exhibits constant reflection characteristics, whereas a surface with defects exhibits changes in reflection characteristics, which can be expressed as a gray value difference that can be detected by the vision camera.

[0117] In the above inspection system, the LED light source irradiates light to the entire surface in the width direction of the electrode at a specific angle (e.g., 30 degrees), and at this time, the LED provides light of uniform intensity and wavelength, so that the characteristics of the reflected light can be controlled consistently. The vision camera detects the light (reflected light) irradiated from the LED light source and reflected from the electrode surface, and records the intensity of the reflected light in pixel units through an image sensor, and the control and analysis software processes the data collected from the vision camera to analyze the reflective characteristics of the electrode surface and can determine whether there is a defect based on the difference in gray values.

[0118] Through the above inspection system, an area where the gray value difference (△GV) is greater than 20 can be identified, and if the major axis length of the horizontal cross-section of the area parallel to the electrode surface is 1.5 mm or longer, this area can be defined as a heterochromatic area. In particular, the heterochromatic area can be defined as extending in the longitudinal direction (MD direction) of the electrode. This is because the heterochromatic area on the electrode surface is formed when one or more foreign substances or aggregates of foreign substances located on or near the electrode surface are pressed in the rolling direction during the calendaring or lamination process during electrode manufacturing, and thus the extension direction of the heterochromatic area is in the longitudinal direction of the electrode.

[0119] If the gray value of the surface of the electrode is 20 or less, the difference in gray values ​​between the background and the defect is practically non-existent, so the electrode surface can be considered to have uniform characteristics without defects. In addition, if the gray value difference is greater than 20, even a small defect is recognized on the surface of the electrode, which may result in a poor appearance of the electrode, problems such as the defective portion sticking to the calendar roll and tearing the film, etc.

[0120] The surface of the electrode of the present invention has 5 / m of these two-color regions. 2 According to one embodiment of the present invention, the surface of the electrode has 0 to 5 such heterochromatic regions / m2 , or 0 to 3 / m 2 can have it.

[0121] The surface of the electrode of the present invention is 5 / m 2 Having the following unusual region means that the electrode surface is virtually free of defects, and thus has excellent appearance characteristics.

[0122] The above-mentioned heterochromatic region may be derived from a single particle of the modified polyolefin or an aggregate of multiple particles of the modified polyolefin. That is, the above-mentioned heterochromatic region may be derived from a single particle of the modified polyolefin or an aggregate of multiple particles of the modified polyolefin that are not sufficiently melted during the mixing process when manufacturing the electrode and remain in the electrode mixed powder, and may be confirmed on the surface of the final electrode as a result of the calendaring process and the lamination process.

[0123] In the present invention, in the case of the modified polyolefin included together with the active material, conductive material, fluorine-based polymer, etc., the size of each particle is large, and the modified polyolefin with such large particles melts and becomes flowable by heat rather than shear force after dispersion, so it has the property of being finely dispersed. Therefore, dispersion through mixing of the modified polyolefin has limitations, and there is a problem of low dispersibility.

[0124] Accordingly, during the final manufacturing of the electrode through processes such as mixing, kneading, crushing, calendering, and lamination of electrode materials, if the initially introduced modified polyolefin is not evenly distributed among other electrode materials and multiple particles of the modified polyolefin clump together to form aggregates, and if the average particle diameter of the initially introduced modified polyolefin itself is very large and is not controlled to a predetermined size or less during the electrode manufacturing process, the final electrode may also have a very large particle diameter, the electrode surface may not be smooth and may have a very poor appearance, such as having protrusions that grow outward or, conversely, having depressions that sink inward.

[0125] To improve the appearance characteristics of these electrodes, the average particle size of the initially introduced modified polyolefin can be controlled to a predetermined range or lower, or the manufacturing process temperature can be increased to melt the modified polyolefin and improve dispersibility. In the latter case, the modified polyolefin melts and flows above its melting point, so the higher the temperature, the better the flowability.

[0126] When the average particle size of the initially introduced modified polyolefin is controlled to be within a predetermined range, the initially introduced modified polyolefin may have an average particle size of 0.5 mm or less, or 10 µm to 0.5 mm, or 10 µm to 450 µm, or 10 µm to 250 µm, or 250 µm to 450 µm.

[0127] That is, the modified polyolefin included in the electrode according to one embodiment of the present invention may be derived from modified polyolefin particles having an average particle diameter of 0.5 mm or less.

[0128] In one embodiment of the present invention, the content of the modified polyolefin may be 2 to 40 parts by weight based on 100 parts by weight of the binder.

[0129] According to one embodiment of the present invention, the content of the modified polyolefin may be 3 to 40 parts by weight, 3.5 to 40 parts by weight, or 4 to 40 parts by weight, or 2 to 33.3 parts by weight, 2 to 30.3 parts by weight, or 3 to 33.3, or 3 to 30.3 parts by weight, or 30.3 to 33.3, based on 100 parts by weight of the binder.

[0130] Additionally, the weight ratio of the modified polyolefin and the fluorinated polymer in the binder may be 2:98 to 30:70, or 3:97 to 40:60.

[0131] When the content of the above-mentioned modified polyolefin satisfies this range, the adhesion between the electrode layer and the current collector can be improved, and the mechanical properties of the electrode film can be improved.

[0132] An electrode according to one aspect of the present invention includes a modified polyolefin including at least one functional group among a carboxylic acid anhydride-derived repeating unit and a carboxylic acid-derived functional group, so that the adhesive strength with a current collector is improved, and when such a modified polyolefin is not sufficiently melted in a mixing process during electrode manufacturing and remains as one or more aggregates, a problem that may affect the appearance characteristics of the electrode surface is improved, so that the particle size of the modified polyolefin or the conditions of the mixing process, etc. are controlled so that the surface of the electrode is 5 / m. 2 It has the following unique areas and can exhibit excellent appearance characteristics.

[0133] Furthermore, in the case of high-temperature treatment in an excessive mixing process to improve the appearance characteristics, the mechanical strength of the final electrode layer may be reduced, which may cause a problem of fracture when transported between rolls without a support during the electrode manufacturing process. However, the electrode according to one aspect of the present invention can exhibit excellent mechanical properties, i.e., a fracture strength per unit width of the electrode layer (electrode film) of 0.6 N / cm or more, along with the above-described excellent electrode surface appearance characteristics, by more closely controlling the conditions such as the melting point of the modified polyolefin and the mixing process.

[0134] The breaking strength per unit width of the electrode layer (electrode film) is 0.6 N / cm or more, and according to one embodiment of the present invention, it may be 0.6 N / cm to 3 N / cm, or 0.7 N / cm to 3 N / cm, or 0.79 N / cm to 3 N / cm, or 0.79 N / cm to 1.5 N / cm, or 0.79 N / cm to 1.16 N / cm, or 0.8 N / cm to 1.16 N / cm, or 0.79 N / cm to 0.8 N / cm. When the breaking strength per unit width of the electrode satisfies this range, the problem of breaking occurring when transporting between rolls without a support during the electrode manufacturing process can be prevented, thereby enabling roll-to-roll manufacturing.

[0135] The breaking strength per unit width of the electrode layer (electrode film) can be evaluated as follows. That is, the electrode film cut into 1 cm X 5 cm is pulled at a speed of 5 cm / min using UTM (Zwick) and the stress and strain are measured, and the maximum stress value just before breaking is the tensile strength (kgf / cm 2 , or MPa), and the tensile strength at this time can be multiplied by the thickness of the electrode film to calculate the breaking strength per unit width of the electrode layer (electrode film).

[0136] According to one embodiment of the present invention, the melt index (MI) of the modified polyolefin may be 50 g / 10 min or less, or 0.5 to 50 g / 10 min, or 1 to 32 g / 10 min, or 1 to 30 g / 10 min, or 1 to 10 g / 10 min, or 10 to 32 g / 10 min.

[0137] When the melt index (MI) of the above modified polyolefin satisfies 50 g / 10 min or less, an appropriate molecular weight of the modified polyolefin is secured, and the adhesive strength between the electrode layer and the current collector can be improved.

[0138] Here, the melt index, also known as the melt index or melt flow index, is one of the characteristics that indicates the rheological properties of a polymer. For example, the melt index can be measured by calculating the weight of a polymer sample that flows out over 10 minutes, and the unit can be g / 10 min.

[0139] According to one embodiment of the present invention, the melt index, or melt index (MI), can be measured by ASTM D-1238 (condition E, 190°C, 2.16 kg load), or can be measured under conditions of 230°C, 2.16 kg load. Specifically, among the above measurement conditions, the former condition (190°C, 2.16 kg load) can be applied to measuring the melt index of a modified polyethylene system, and the latter condition (230°C, 2.16 kg load) can be applied to measuring the melt index of a modified polypropylene system.

[0140] According to one embodiment of the present invention, the melting point of the modified polyolefin may be 140°C or less, or 70°C to 140°C, or 73°C to 140°C, or 70°C to 135°C, or 70°C to 130°C, or 73°C to 130°C, or 73°C to 128°C, or 73°C to 124°C, or 124°C to 128°C.

[0141] In order to apply the modified polyolefin to an electrode in one embodiment of the present invention, the modified polyolefin must be melted and evenly dispersed and mixed with other electrode materials in the kneading step of the electrode manufacturing method described below. Therefore, when setting the kneading temperature, it is necessary to consider the melting point of the modified polyolefin.

[0142] For example, if the kneading temperature is raised above the melting point of the modified polyolefin, the appearance of the electrode film and the film-collector adhesion can be improved to some extent, but if the kneading temperature is raised excessively, the mechanical strength of the electrode film may be reduced.

[0143] That is, when applying a modified polyolefin having a high melting point to an electrode, the mixing temperature must be raised higher than the melting point of the modified polyolefin so that the modified polyolefin melts under mixing conditions and is evenly dispersed and mixed with other electrode materials. At this time, the modified polyolefin melts and there is no problem, but if the mixing temperature is too high, the fiberization of the fluorinated binder (e.g., PTFE) may proceed excessively, so that the fibers of the polymer of the fluorinated binder may continue to become thinner and eventually break, which may lower the strength of the electrode film.

[0144] On the other hand, if the melting point of the modified polyolefin is controlled to be 140°C or lower, the mixing temperature can be controlled to a relatively low temperature, for example, 170°C or lower, or 160°C or lower, or 150°C or lower, during the mixing process, thereby preventing excessive fiberization of the fluorine-based binder and providing an electrode film with excellent mechanical strength.

[0145] At this time, the melting point of the modified polyolefin can be measured using a Differential Scanning Calorimeter (DSC, device name: DSC 2920, manufacturer: TA instrument). Specifically, the polymer is heated to 220°C, maintained at that temperature for 5 minutes, cooled to 20°C, and then increased again. At this time, the temperature increase and decrease rates can each be controlled to 10°C / min.

[0146] According to one embodiment of the present invention, the content of the active material may be 80 to 98 parts by weight, the content of the conductive material may be 0.5 to 10 parts by weight, the content of the fluorinated polymer may be 0.5 to 5 parts by weight, and the content of the modified polyolefin may be 0.02 to 3.3 parts by weight.

[0147] In addition, the content of the active material may be 90 to 98 parts by weight, or 90 to 96 parts by weight, the content of the conductive material may be 0.5 to 7 parts by weight, or 0.5 to 1 part by weight, or 1 to 7 parts by weight, the content of the fluorinated polymer may be 0.5 to 4.5 parts by weight, or 0.5 to 2 parts by weight, or 2 to 4.5 parts by weight, or 0.5 to 2.3 parts by weight, or 2 to 2.3 parts by weight, or 2.3 to 4.5 parts by weight, and the content of the modified polyolefin may be 0.02 to 3 parts by weight, or 0.02 to 2.5 parts by weight, or 0.03 to 2 parts by weight, 0.02 to 1 part by weight, or 1 to 3 parts by weight.

[0148] When the contents of the above active material, conductive material, binder, and modified polyolefin satisfy these ranges, the binder can be sufficiently fiberized in a subsequent mixing process to form a mixture lump, and an electrode film can be easily manufactured through the molding of the mixed powder formed through a grinding process, the physical properties of the electrode film can be secured, the content of the active material is secured to prevent the problem of capacity reduction, and sufficient conductivity can be secured.

[0149] Meanwhile, in some cases, a filler, which is a component that suppresses expansion of the electrode, may be additionally added to the electrode layer. The filler is not particularly limited as long as it is a fibrous material that does not cause a chemical change in the battery, and for example, olefin polymers such as polyethylene and polypropylene; and fibrous materials such as glass fiber and carbon fiber are used.

[0150] The current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. The current collector can also form fine unevenness on its surface to increase the adhesive strength of the positive electrode active material, and various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric are possible.

[0151] As described above, the electrode layer of the electrode of the present invention includes a modified polyolefin including at least one functional group among a carboxylic anhydride-derived repeating unit and a carboxylic acid-derived functional group, and since at least one functional group among the carboxylic anhydride-derived repeating unit and the carboxylic acid-derived functional group of the modified polyolefin has excellent reactivity, the electrode layer including the modified polyolefin has greatly improved adhesion to a current collector. Therefore, the current collector used in the electrode of one embodiment of the present invention can secure excellent adhesion and interface resistance characteristics between the electrode layer and the current collector without the need for a separate primer layer.

[0152] The porosity of the electrode layer of the above electrode may be 20 to 50%, or 20 to 45%, or 20 to 40%, or 20 to 35%, or 22 to 30%, or 20 to 28%, or 20 to 26%, or 23.1 to 27.4%, or 23.1 to 24.8%, 23 to 26%, or 24.8 to 27.4%. This porosity may vary slightly depending on which effect is focused on, etc.

[0153] However, when the porosity of the electrode layer is within this range, the electrolyte impregnation property is improved, so that the life characteristics and output characteristics are excellent, and the volume does not need to increase to express the same capacity, so it is advantageous in terms of energy density per volume.

[0154] The porosity of the electrode layer can be obtained by measuring the apparent density of the composite film alone by subtracting the volume and weight of the current collector from the volume and weight of the electrode, and using the actual density calculated based on the actual density and composition of each component, using the following relationship.

[0155] Porosity (%) = {1 - (Apparent density / Actual density)} X 100

[0156] In one embodiment of the present invention, the crystallinity of the binder in the electrode layer may be 10% or less.

[0157] In the present invention, the crystallinity (Xc) can be measured through differential scanning calorimetry (DSC), and is based on the temperature (peak temperature) at which the highest enthalpy is observed during crystallization. Specifically, the crystallinity is measured by the melting enthalpy (△H) actually measured in DSC. m ) value is theoretically the melting enthalpy (△H) of a perfect crystal (crystallization degree 100%) m 0 )(equilibrium heat of fusion) and expressed as a %, which can be calculated by the following equation 1. Here, the theoretical melting enthalpy value of a perfect crystal can be found and used in the polymer handbook for known polymers, and for unknown or newly synthesized substances, it can be calculated by the extrapolation method that extends the crystallinity by two or more points.

[0158] [Relationship 1]

[0159] Xc(%) = (△H m / △H m 0) X 100

[0160]

[0161] The above electrode layer may be derived from a film for a dry electrode. The term "film for a dry electrode" refers to a film manufactured by a dry manufacturing method that does not use a dispersion medium, unlike a wet electrode manufacturing method in which an active material, a conductive material, and a binder are dissolved and / or dispersed in a dispersion medium such as water or an organic solvent during conventional electrode manufacturing, and the resulting slurry is applied onto a current collector and then dried. The electrode film manufactured in this manner is then laminated onto a current collector to ultimately be manufactured into an electrode. The specific manufacturing method of the electrode film and the electrode will be described below.

[0162]

[0163] According to one aspect of the present invention,

[0164] A step of preparing a mixture comprising an active material, a conductive material, and a binder, wherein the binder comprises a fluorinated polymer and a modified polyolefin;

[0165] A step of kneading the mixture at a temperature ranging from 70°C to 170°C and under a pressure higher than atmospheric pressure to produce a mixture lump;

[0166] A step of crushing the above mixture lump to obtain a mixed powder for electrode;

[0167] A step of forming an electrode film by injecting the above electrode-use mixed powder between a plurality of rolls and performing a calendaring process; and

[0168] A method for manufacturing an electrode according to one embodiment of the present invention is provided, characterized in that it includes a step of laminating the above electrode film on a metal current collector.

[0169]

[0170] Hereinafter, a method for manufacturing an electrode according to one embodiment of the present invention will be described in more detail.

[0171] First, a mixture containing an active material, a conductive material, and a binder is prepared. The binder includes a fluorinated polymer and a modified polyolefin.

[0172] At this time, the mixing for manufacturing the mixture is performed so that the active material, conductive material, and binder can be uniformly distributed, and since they are mixed in powder form, there are no limitations as long as they enable simple mixing thereof, and the mixing can be performed by various methods. However, since the electrode of the present invention is manufactured by a dry manufacturing method that does not use a dispersion medium, the mixing can be performed by dry mixing, and can be performed by putting the materials into a device such as a blender.

[0173] According to one embodiment of the present invention, in the step of preparing a mixture including the active material, the conductive material, and the binder, the modified polyolefin included in the binder may have an average particle size of 0.5 mm or less, or 10 µm to 0.5 mm, or 10 µm to 450 µm, or 10 µm to 250 µm, or 250 µm to 450 µm. When the average particle size of the modified polyolefin satisfies this range, the modified polyolefin is advantageously able to improve dispersibility with other electrode materials during the preparation of the mixture.

[0174] In addition, the above mixture can be prepared by mixing in a mixer at 5,000 rpm to 20,000 rpm for 30 seconds to 2 minutes, specifically at 10,000 rpm to 15,000 rpm for 30 seconds to 1 minute, to ensure uniformity.

[0175] According to one embodiment of the present invention, a super mixer or the like can be used in the mixing step of preparing the mixture, and specifically, a method of mixing in a super mixer at 1,000 to 2,000 rpm for 2 to 10 minutes can be applied.

[0176] The above fluorine-based binder can be microfiberized by the step of manufacturing the above mixed powder. Microfiberization refers to a process of dividing a polymer into fine particles and can be performed using, for example, mechanical shear force. Specific examples of such binders are as described above.

[0177]

[0178] Next, the mixture is kneaded at a temperature ranging from 70°C to 170°C and under a pressure higher than atmospheric pressure to produce a mixture lump.

[0179] In conventionally known techniques, high-shear mixing, such as in a jet mill, is performed to fiberize a fluorine-based binder. However, problems arise in that the active material is finely divided by the mixing and the formed fibers may be cut. In the present invention, the above problems are solved by a low-shear kneading method rather than high-shear mixing.

[0180] The above mixing is not limited to a specific method. In a specific embodiment of the present invention, the mixing may be performed using a kneader, for example.

[0181] This mixing step is a step in which the fluorine-based binder fiberizes and combines or links the active material, conductive material, and modified polyolefin to form a 100% solids mixture mass. In addition, during this mixing step, the temperature must be raised above the melting point of the modified polyolefin so that the modified olefin melts and the dispersibility of the mixing target can be improved.

[0182] Specifically, the mixing can be controlled at a speed of 10 rpm to 100 rpm. For example, the mixing can be controlled at a speed of 20 rpm or more or 70 rpm or less within the above range. The mixing can be performed for 1 minute to 30 minutes.

[0183] For example, the mixing can be performed for 3 to 30 minutes at a speed of 20 to 50 rpm within the above range. Meanwhile, the mixing can be controlled at a shear rate of 10 / s to 500 / s. In a specific embodiment of the present invention, the mixing can be performed for 1 to 30 minutes, and the shear rate can be controlled at a range of 30 / s to 100 / s.

[0184] Additionally, this mixing step can be performed under conditions of high temperature and pressure higher than atmospheric pressure, and more specifically, under conditions of pressure higher than atmospheric pressure.

[0185] More specifically, the mixing may be performed at a temperature of from 70°C to 170°C, specifically from 90°C to 170°C, or from 90°C to 160°C, or from 90°C to 150°C.

[0186] If the process is performed at a low temperature below 70°C outside the above temperature range, the fiberization and lump formation by the kneading of the binder during kneading are not performed well, so film formation is not easily performed during calendaring, and if the process is performed at an excessively high temperature exceeding 170°C, the fiberization of the binder occurs rapidly and there is a problem that the already formed fibers may be cut by excessive shear force thereafter, which is not preferable.

[0187] Additionally, it can be performed at a pressure higher than atmospheric pressure, or under a pressure of 1 atm (atmospheric pressure) to 60 atm, or under a pressure of 1 atm to 30 atm, or under a pressure of 1 atm to 10 atm, or under a pressure of 1 atm to 8 atm, or under a pressure of 1.1 atm to 7 atm, or under a pressure of 1.1 atm to 6 atm.

[0188] When the above pressure range is satisfied, problems such as fibers being cut or the density of the mixture mass becoming too high due to the application of excessive shear force and pressure can be prevented. That is, according to the present invention, the intended effects of the present invention can be achieved when a low-shear mixing process is performed under conditions of high temperature and pressure above normal pressure instead of high-shear mixing.

[0189] In addition, according to one embodiment of the present invention, in order to improve the dispersibility of the modified polyolefin, a method may be performed in which a part of the active material or a part of the conductive material and the modified polyolefin are mixed and kneaded in advance, and the resultant product thus mixed and kneaded is again mixed and kneaded with the remaining electrode materials.

[0190] Next, the above mixture lump is pulverized to obtain a mixed powder for electrodes.

[0191] Specifically, the mixture lump manufactured through the above mixing may be directly calendered, but in this case, the mixture lump may have to be pressed to manufacture it into a thin film form, and thus, a problem may arise in that a uniform film cannot be obtained. Therefore, according to the present invention, the manufactured mixture lump undergoes the pulverization step. That is, if the electrode-use mixture powder obtained through pulverization is too large or clumped, a bridge may be formed during the calendering process, causing a defect in the film appearance such as a pinhole, or a film with uneven surface characteristics may be generated. Therefore, a electrode-use mixture powder having a uniform size is obtained through pulverization, and then calendering is performed.

[0192] At this time, the grinding step is not limited, but can be performed with a device such as a blender or grinder, and the grinding step can be specifically performed at a speed of 5,000 rpm to 20,000 rpm for 30 seconds to 10 minutes, and specifically at a speed of 10,000 rpm to 18,000 rpm for 30 seconds to 2 minutes.

[0193] When the above grinding speed and time are satisfied, sufficient grinding can be achieved to form powder of a size suitable for filming, and the problem of excessive fine particles being generated in the mixture mass can be prevented. If necessary, a classification process can be performed to filter out powder exceeding a certain size or powder below a certain size.

[0194] According to one embodiment of the present invention, a cutter mill, a fine mill, etc. may be used in the pulverizing step. At this time, the cutter mill may be used to coarsely pulverize the mixture lump produced by kneading to a size of several mm by operating at a condition of 400 to 500 rpm for several seconds. In addition, the fine mill may be used to uniformly pulverize the coarsely pulverized powder to a size below a certain level, and may be used at a condition of 3,000 to 8,000 rpm.

[0195] Next, the above electrode-use mixed powder is fed between a plurality of rolls and subjected to calendaring processing to form an electrode-use film.

[0196] Referring to FIGS. 1A and 1B, a process (100) for forming a film for an electrode is performed by placing a plurality of rolls (110) spaced apart from each other, inserting a mixed powder for an electrode (120) obtained in a previous step between adjacent rolls (100), and rotating the rolls (100) in an facing direction so that the mixed powder (120) is rolled and formed into a sheet or film form through a powder sheeting step, and then, through a plurality of calenderings, a film for an electrode having a final target thickness can be obtained.

[0197] According to one embodiment of the present invention, in the process of forming an electrode film, the spacing between a plurality of rolls can be appropriately controlled in consideration of the specifications and physical properties of the electrode film being manufactured. For example, compared to FIG. 1a, in FIG. 1b, the spacing between the second and third rolls and the spacing between the fourth and fifth rolls can be controlled to be larger.

[0198] Specifically, such calendaring may be a step of processing the mixed powder for the electrode into a film form, for example, manufacturing it into a film form with an average thickness of 50 ㎛ to 300 ㎛.

[0199] At this time, the calendaring may be performed, for example, by a roll that is present in contact with the substrate. According to one embodiment of the present invention, the calendaring may be performed repeatedly one or more times, for example, one to five times, or three to four times, or four times.

[0200] At this time, the roll temperature can be 50℃ to 200℃.

[0201] The rotation speed ratio of the above roll can be appropriately controlled depending on the size of the roll, the number of calendaring cycles, and the thickness of the electrode film, and can be controlled in the range of, for example, 1 to 10 times, or 1 to 8 times, or 1 to 7 times, or 1.2 to 5 times.

[0202] Additionally, the spacing between the facing rolls can be variably adjusted depending on the thickness and density of the film to be obtained.

[0203] By proceeding to this calendering step, a dry electrode film that functions as an electrode mixture can be manufactured. Such dry electrode films are also conventionally referred to as free-standing films.

[0204] The electrode film manufactured in this manner does not contain a solvent, has almost no fluidity, and is thus easy to handle and can be processed into a desired shape to be used in the manufacture of various types of electrodes. Furthermore, if the electrode film of the present invention is used in the manufacture of electrodes, the drying process for solvent removal can be omitted, so not only can the manufacturing process of the electrode be significantly improved, but also problems such as breakage of the active material or disconnection of the fiberized binder contained therein, which were problems in the manufacture of existing dry electrodes, can be solved.

[0205] Meanwhile, in the present invention, the film for electrodes may have a porosity of 20% to 50%, and preferably, within the above range, may be controlled to a value of 40% or less or 30% or less. When the porosity satisfies this range, electrolyte impregnation is easy, so that life characteristics and output characteristics can be improved, and the volume does not need to increase to express the same capacity, so that the energy density per volume can be improved. In one embodiment of the present invention, the porosity can be obtained by the following equation by measuring the apparent density of the film for dry electrodes and using the actual density calculated based on the actual density and composition of each component.

[0206] Porosity (%) = {1 - (apparent density / actual density)} x 100

[0207]

[0208] Next, the above electrode film is laminated onto a metal current collector.

[0209] The above lamination step may be a step of rolling and attaching the electrode film obtained in the previous step to a predetermined thickness on a current collector. The lamination may also be performed using a lamination roll, and at this time, the lamination roll may be maintained at a temperature of 25°C to 250°C.

[0210] According to one embodiment of the present invention, a lamination step may be performed sequentially after the calendering step. Specifically, when the calendering and lamination steps are performed sequentially, a method may be employed in which a film is manufactured with a porosity of less than 30% before the lamination step, the film is laminated, and no additional rolling is performed.

[0211] Referring to FIG. 3, the electrode-use mixed powder (1) obtained by crushing a mixture lump is fed (300) through a powder feeder (310) and a supply roller (320), thereby forming an initial sheet (10), and then forming an electrode-use film (410) through a calendaring roll (411, 412), and the electrode-use film (410) is laminated onto a metal current collector (20) supplied from a current collector winding roll (50) to be provided as a final electrode winding roll (60). At this time, the calendaring roll (412) can perform a lamination process together with the lamination roll (500).

[0212] Referring to Fig. 4, a powder mixture (1) for electrodes obtained by crushing a mixture lump is fed (300) through a powder feeder (310) and a supply roller (320), passes through a plurality of calendaring rolls (400), forms an electrode film, and laminates the electrode film on a metal current collector supplied from a current collector winding roll (50) to be provided as a final electrode winding roll (60). At this time, among the continuous calendaring rolls, the last calendaring roll can perform a lamination process together with the lamination roll (500).

[0213] As described above, the electrode layer of the electrode of the present invention includes a modified polyolefin including at least one functional group among a carboxylic anhydride-derived functional group and a carboxylic acid-derived functional group, and since at least one functional group among the carboxylic anhydride-derived functional group and the carboxylic acid-derived functional group of the modified polyolefin has excellent reactivity, the electrode layer including the modified polyolefin can have significantly improved adhesion to a current collector. Therefore, the current collector used in the electrode of one embodiment of the present invention can be applied without the need for a separate primer layer.

[0214]

[0215] According to one embodiment of the present invention, the compression ratio of the electrode film may be 30 to 50%, or 35 to 50%, or 40 to 50%.

[0216] The compression ratio of the above electrode film can be defined as the ratio of the thickness to which the electrode film is compressed at the moment of lamination, and can be expressed by the following equation 1.

[0217] [Formula 1]

[0218] Compression ratio (%) = T p / T1Х100

[0219] In equation 1,

[0220] T p In the lamination step, it refers to the pressing thickness of the film for electrodes,

[0221] T1 refers to the thickness of the electrode film before the lamination step.

[0222] In the present invention, by controlling the compression ratio in the lamination step to satisfy a specific range, it is possible to provide an appropriate density and porosity of the electrode film and excellent adhesion between the electrode film and the current collector.

[0223] When the compression ratio of the electrode film satisfies the range of 30 to 50%, the pressure applied to the electrode film is sufficient to improve the adhesive strength between the electrode film and the current collector, the problem of the electrode film being peeled off from the current collector after the lamination process can be prevented, and the problem of the density of the electrode film being increased more than necessary, resulting in a low porosity compared to the target porosity or damage to the current collector can be resolved.

[0224] In one embodiment of the present invention, when laminating an electrode film on both sides of the current collector, the compression ratio (%) of the above formula 1 may mean the following formula 2.

[0225] [Formula 2]

[0226] 30 ≤(T1+ 0.5T c - 0.5T gap) / T1Х 100 ≤50

[0227] In Equation 2, T1 represents the thickness of the electrode film before the lamination step, and T c refers to the thickness of the entire house, and T gap refers to the spacing between the first and second rolling rolls.

[0228]

[0229] Additionally, the rolling ratio of the electrode film that has undergone the lamination step may be in the range of 20% or less, or 18% or less, or 15% or less, or 5% to 15%, or 6% to 15%, or 7% to 15%, or 9% to 13%.

[0230] Here, the rolling ratio can be defined as the ratio of the thickness of the electrode film after the lamination step to the thickness of the electrode film before the lamination step, and can be expressed by Equation 3 below.

[0231] [Formula 3]

[0232] Rolling rate (%) = (T1-T2) / T1Х100

[0233] In the above equation 3,

[0234] T1 refers to the thickness of the electrode film before the lamination step,

[0235] T2 represents the thickness of the electrode film after the lamination step.

[0236] When the above rolling ratio satisfies the above-described range, an appropriate density and porosity of the electrode film and an adhesive strength between the electrode film and the current collector can be achieved.

[0237]

[0238] The apparent density increase rate before and after lamination of the above electrode film with the current collector can be expressed by the following equation 4:

[0239] [Formula 4]

[0240] Apparent density increase rate (%) = (D2-D1) / D1Х 100

[0241] D1 is the apparent density (g / cm) of the electrode film before the lamination step. 3 ) represents,

[0242] D2 is the apparent density (g / cm) of the electrode film after the lamination step. 3 ) is indicated.

[0243] The apparent density increase rate before and after lamination of the above electrode film with the current collector may be 5 to 30%, or 7 to 25%, or 10 to 20%.

[0244] D1 and D2, which represent the apparent density of the film for the electrode, can be varied depending on the type of active material, and according to one embodiment of the present invention, the active material is lithium nickel-manganese-cobalt oxide Li 1+x (Ni a Co b Mn c ) 1-x O2(x = 0 ~ 0.03, a = 0.3 ~ 0.95, b = 0.01 ~ 0.35, c = 0.01 ~ 0.5, a+b+c=1); or lithium nickel-manganese-cobalt oxide partially substituted with aluminum (lithium nickel-manganese-cobalt-aluminum oxide) Li a [Ni b Co c Mn d Al e ] 1-f M 1 f O 2 ( Above M 1 is at least one selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P and S, and 0.8≤a≤1.2, 0.5≤b≤0.99, 0 <c<0.5, 0<d<0.5, 0.01≤e≤0.1, 0≤f≤0.1임) 등 인 경우에, 상기 D1및 D2는 2.75 g / cm 3 3.75 g / cm 3 It could be a range.

[0245] Meanwhile, when the apparent density increase rate of the electrode film satisfies the above range, the adhesion between the electrode film and the current collector can be improved, and the problem of the porosity going beyond the target range or the positive electrode active material or the current collector being damaged can be prevented.

[0246] The apparent density before and after lamination of the electrode film with the current collector can be calculated by measuring the weight and thickness of the electrode film before lamination, measuring the weight and thickness of the electrode after lamination, and subtracting the weight and thickness of the current collector from the weight and thickness of the film.

[0247] In addition, the active material loading amount of the film for the dry electrode is 3 mAh / cm 2 Up to 15 mAh / cm 2 It can be 4 mAh / cm in detail. 2 10 mAh / cm 2 It could be.

[0248] Here, the loading amount of the active material is a value calculated using the following equation 5.

[0249] [Formula 5]

[0250] Loading amount of active material (mAh / cm) 2 ) = Capacity of active material (mAh / g) x Weight content ratio of active material in dry electrode film (wt%) x Weight per unit area of ​​dry electrode film (g / cm 2 )

[0251]

[0252] In addition, the interfacial resistance (resistance before immersion in electrolyte, initial resistance) between the electrode film and the current collector is 1 Ω·cm. 2 or less, or 0.8 Ω·cm 2 or less, or 0.7Ω·cm 2 or less, or 0.5 Ω·cm 2 or less, or 0.29Ω·cm 2 or less, or 0.20 to 1Ω·cm 2 , or 0.20 to 0.29Ω·cm 2It can be. Here, the interfacial resistance can be calculated by applying a current of 100 ㎂ to the electrode using the MP (Multi Probe) resistance measurement method and measuring the resistance value between the dry electrode film and the contact layer with the potential difference measured between multiple probes. If the range of the interfacial resistance is satisfied, the battery performance of the secondary battery manufactured thereafter can be improved.

[0253] In addition, according to one embodiment of the present invention, the interfacial resistance between the electrode film and the current collector after immersion of the electrode in the electrolyte is 1.0 Ω·cm. 2 or less, or 0.8 Ω·cm 2 or less, or 0.7 Ω·cm 2 or less, or 0.3 to 1.0 Ω·cm 2 , or 0.32 to 1.0 Ω·cm 2 , or 0.32 to 0.69 Ω·cm 2 It could be.

[0254] At this time, the interfacial resistance between the electrode film and the current collector after immersion in the electrolyte solution can be calculated by preparing a liquid electrolyte in which 1 M LiPF6 is dissolved in a solvent in which ethylene carbonate, dimethylene carbonate, and diethyl carbonate are mixed in a volume ratio of 1:2:1, immersing the electrode for one week, then taking it out, applying a current of 100 μA using the MP (Multi Probe) resistance measurement method, and measuring the resistance value between the dry electrode film and the current collector layer by the potential difference measured between multiple probes.

[0255]

[0256] According to one embodiment of the present invention, the adhesive strength (initial adhesive strength, adhesive strength before immersion in electrolyte) of the electrode may be 38 gf / 2cm or more, or 50 gf / 2cm or more, or 50 gf / 2cm to 500 gf / 2cm, or 150 gf / 2cm to 250 gf / 2cm, or 162 gf / 2cm to 212 gf / 2cm.

[0257] At this time, the adhesive strength of the electrode can be measured by attaching double-sided tape to a slide glass, placing an electrode sample with a predetermined size (e.g., 20 mm X 100 mm) of electrode on it, and adhering it by rolling it back and forth 10 times with a 2 kg roller, and then removing air bubbles using a laminating machine with a gap of 5 mm and a speed of 5 mpm, and then pulling it at 100 mm / min using a UTM (TA) device to measure the adhesive strength as the peeling force from the slide glass. At this time, the measurement angle between the slide glass and the electrode can be 90°.

[0258] According to one embodiment of the present invention, the adhesive strength of the electrode after immersion in the electrolyte may be 38 gf / 2cm or more, or 50 gf / 2cm or more, or 150 gf / 2cm or more, or 50 gf / 2cm to 500 gf / 2cm, or 150 gf / 2cm to 300 gf / 2cm, or 170 gf / 2cm to 250 gf / 2cm, or 174 gf / 2cm to 233 gf / 2cm.

[0259] At this time, the adhesive strength of the electrode after immersion in the electrolyte is prepared by dissolving 1M LiPF6 in a solvent in which ethylene carbonate, dimethylene carbonate, and diethyl carbonate are mixed in a volume ratio of 1:2:1, and the electrode is immersed for 1 week, then taken out, washed with a DMC solution, and dried, and a positive electrode sample punched out to a predetermined size (e.g., 20 mm X 100) mm is placed on it, and bonded by reciprocating 10 times with a 2 kg roller, and then, after removing air bubbles using a laminating machine with a gap of 5 mm and a speed of 5 mpm, the adhesive strength can be measured by the force of peeling from a slide glass using a UTM (TA) device at 100 mm / min. At this time, the measurement angle between the slide glass and the electrode can be 90°.

[0260] When the adhesive strength of the electrode after immersion in the electrolyte satisfies this range, no lifting occurs on the appearance of the electrode layer even after the electrode is immersed in the electrolyte, so there is no detachment phenomenon or bubble generation in the electrode layer, and the adhesive strength can be maintained even after immersion in the electrolyte.

[0261] Figure 2 is a schematic diagram of a step of laminating an electrode film on both sides of a current collector according to one embodiment of the present invention. That is, the lamination step (200) can ultimately obtain an electrode (240) by rolling and attaching the electrode film (230) obtained in the previous step to a predetermined thickness on a current collector (220) using a pair of lamination rolls (210).

[0262] According to another embodiment of the present invention, an electrode manufactured by the method for manufacturing the electrode is provided. In addition, a secondary battery including the electrode is provided, wherein the electrode is a positive electrode, and an electrode assembly including the positive electrode, the negative electrode, and a separator is housed in a battery case (cylindrical case, square case, pouch, etc.) together with a lithium-containing non-aqueous electrolyte, and an energy storage device including the same as a unit battery is provided.

[0263]

[0264] At this time, since the specific structure of the secondary battery and energy storage device is known in the prior art, a description thereof is omitted in this specification.

[0265] Meanwhile, according to one embodiment of the present invention, a dry electrode manufacturing apparatus is provided, comprising: a blender for mixing raw materials for a composite including an active material, a conductive material, a binder, and a modified polyolefin; a kneader for kneading the mixture to form a mixture lump; a crusher for crushing the mixture lump to form a mixed powder for an electrode; a calender for forming the mixed powder for an electrode into a dry electrode film; and a lamination roll for positioning and laminating the dry electrode film on at least one surface of a current collector.

[0266] The above blender is a mixer that mixes raw materials, and can mix the composite raw materials at a speed of 5,000 rpm to 20,000 rpm as described above. A super mixer or the like can be used as the mixer.

[0267] The above kneader is a device for dispersing the fiberization and compounding raw materials of the binder in the present invention, and the mixture can be obtained as a mixture lump through mixing in the kneader. At this time, the kneader for obtaining the result according to the present invention can be performed at a temperature range of 70°C to 170°C, or 90°C to 170°C, or 90°C to 160°C, or 90°C to 150°C, and at a pressure higher than atmospheric pressure, or 1 atm (atmospheric pressure) to 60 atm, or 1 atm to 30 atm, or 1 atm to 10 atm, or 1 atm to 8 atm, or 1.1 atm to 7 atm, or 1.1 atm to 6 atm.

[0268] The above pulverizer is a device that pulverizes such a mixture lump to form a mixed powder for an electrode. A blender can also be used, or a grinder, etc. can be used. Examples of the grinder include a cutter mill and a fine mill.

[0269] The above calendar is a device for forming the mixed powder for the electrode into a film form, and may be, for example, a pair of facing rollers, and the thickness of the film can be controlled from the gap between them.

[0270] The above lamination roll serves to attach and roll a dry electrode film formed by the above calendar to at least one surface of the current collector.

[0271] The porosity of the film for dry electrode according to the present invention can be determined by these calendars and lamination rolls.

[0272] That is, the manufacturing device for a dry electrode according to the present invention is characterized by including a kneader and a crusher.

[0273] The specific structures of the above blender, kneader, calendar, lamination roll, etc. are known in the art, and thus a detailed description thereof is omitted in this specification.

[0274]

[0275] Hereinafter, the present invention will be described in detail with examples to specifically illustrate it. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention should not be construed as being limited to the examples described below. These examples are provided to more fully explain the present invention to those of average skill in the art.

[0276]

[0277] Example 1

[0278] Lithium nickel cobalt manganese aluminum oxide (NCMA, Li[Ni)) as the cathode active material 0.88 Co 0.07 Mn 0.04 ]Al 0.01O2) 96g, 1g of carbon black as a conductive agent, 2g of polytetrafluoroethylene (PTFE) as a binder, and 1g of a polyethylene copolymer (Clariant, MA4351) (Tm 124℃, Melt Index 10g / 10min (measured under 190℃, 2.16kg conditions)) containing a maleic anhydride-derived functional group as a modified polyolefin were placed in a blender and mixed at 10,000 rpm for 1 minute to prepare a mixture, and the resultant was placed in a kneader. At this time, the average particle diameter (D50) of the polyethylene copolymer containing a maleic anhydride-derived functional group as a modified polyolefin was 250㎛.

[0279] The temperature of the kneader was stabilized at 150°C, and the mixture was placed in a pressurized kneader and operated at a speed of 40 rpm for 5 minutes under a pressure of about 1.1 atm to obtain a mixture lump. The mixture lump was placed in a blender, ground at 10,000 rpm for 30 seconds, and classified through a sieve with pores of 1 mm in size to obtain a mixed powder for electrodes. Thereafter, the prepared mixed powder for electrodes was placed in a wrap calender (roll diameter: 160 mm, roll temperature: 100°C) to produce a film, and then calendering was repeated twice to finally produce an electrode film. Two sheets of the electrode films thus prepared were placed on both sides of aluminum foil (thickness: 19 μm) not coated with a primer layer, and laminated through a compression roll maintained at 150°C to produce an electrode (positive electrode).

[0280] The total thickness of the final manufactured electrode was 171 μm, and the thickness of the active material layer formed on one side of the active material layers provided on both sides of the current collector was 76 μm.

[0281]

[0282] Example 2

[0283] Lithium nickel cobalt manganese aluminum oxide (NCMA, Li[Ni)) as the cathode active material 0.88 Co 0.07 Mn 0.04 ]Al0.01 O2) 96g, 1g of carbon black as a conductive agent, 2g of polytetrafluoroethylene (PTFE) as a binder, and 1g of a polyethylene copolymer (Woosung Chemical, SP1750) (Tm 128℃, Melt Index 3g / 10min (measured under 190℃, 2.16kg conditions)) containing a maleic anhydride-derived functional group as a modified polyolefin were placed in a blender and mixed at 10,000 rpm for 1 minute to prepare a mixture, and the resultant was placed in a kneader. At this time, the average particle diameter (D50) of the polyethylene copolymer containing a maleic anhydride-derived functional group as a modified polyolefin used was 500㎛ (the initial average particle size of 2mm was controlled to 450㎛ using a grinder and used).

[0284] The temperature of the kneader was stabilized at 150°C, and the mixture was placed in a pressurized kneader and operated at a speed of 40 rpm for 5 minutes under a pressure of about 1.1 atm to obtain a mixture lump. The mixture lump was placed in a blender, ground at 10,000 rpm for 30 seconds, and classified with a sieve having pores of 1 mm in size to obtain a mixed powder for electrodes. Thereafter, the prepared mixed powder for electrodes was placed in a wrap calender (roll diameter: 160 mm, roll temperature: 100°C) to produce a film, and then calendered twice repeatedly to finally produce an electrode film. Two sheets of the electrode films thus prepared were placed on both sides of aluminum foil (thickness: 19 μm) not coated with a primer layer, and laminated through a compression roll maintained at 150°C to produce an electrode (positive electrode).

[0285] The total thickness of the final manufactured electrode was 173 μm, and the thickness of the active material layer formed on one side of the active material layers provided on both sides of the current collector was 77 μm.

[0286]

[0287] Example 3

[0288] Lithium nickel cobalt manganese aluminum oxide (NCMA, Li[Ni)) as the cathode active material 0.88 Co 0.07 Mn 0.04 ]Al 0.01 O2) 95.7g, carbon black 1g as a conductive agent, polytetrafluoroethylene (PTFE) 2.3g as a binder, polyethylene copolymer containing a maleic anhydride-derived functional group as a modified polyolefin (Clariant, Celldust 8020) (Tm 73℃, Melt Index 32g / 10min (measured under 190℃, 2.16kg conditions)) 1g were put into a blender and mixed at 10,000 rpm for 1 minute to prepare a mixture, and the resultant was put into a kneader, except that the electrode film and electrode (positive electrode) were manufactured in the same manner as in Example 1. At this time, the average particle diameter (D50) of the polyethylene copolymer containing a maleic anhydride-derived functional group as a modified polyolefin used was 10㎛.

[0289]

[0290] The total thickness of the final manufactured electrode was 173 μm, and the thickness of the active material layer formed on one side of the active material layers provided on both sides of the current collector was 77 μm.

[0291]

[0292] Comparative Example 1

[0293] Lithium nickel cobalt manganese aluminum oxide (NCMA, Li[Ni)) as the cathode active material 0.88 Co 0.07 Mn 0.04 ]Al 0.01O2) 95.7g, 1g of carbon black as a conductive agent, 2.3g of polytetrafluoroethylene (PTFE) as a binder, and 1g of a polyethylene copolymer (Woosung Chemical, SP3789) (Tm 165℃, Melt Index 3g / 10min (measured under 230℃, 2.16kg conditions)) containing a maleic anhydride-derived functional group as a modified polyolefin were placed in a blender and mixed at 10,000 rpm for 1 minute to prepare a mixture, and an electrode was manufactured in the same manner as in Example 1. At this time, the average particle diameter (D50) of the polypropylene copolymer containing a maleic anhydride-derived functional group as a modified polyolefin used was 450㎛.

[0294] The temperature of the kneader was stabilized at 150°C, and the mixture was placed in a pressurized kneader and operated at a speed of 40 rpm for 5 minutes under a pressure of about 1.1 atm to obtain a mixture lump. The mixture lump was placed in a blender, ground at 10,000 rpm for 30 seconds, and classified with a sieve having pores of 1 mm in size to obtain a mixed powder for electrodes. Thereafter, the prepared mixed powder for electrodes was placed in a wrap calender (roll diameter: 160 mm, roll temperature: 100°C) to produce a film, and then calendered twice repeatedly to finally produce an electrode film. Two sheets of the electrode films thus prepared were placed on both sides of aluminum foil (thickness: 19 μm) not coated with a primer layer, and laminated through a compression roll maintained at 150°C to produce an electrode (positive electrode).

[0295] The total thickness of the final manufactured electrode was 173 μm, and the thickness of the active material layer formed on one side of the active material layers provided on both sides of the current collector was 77 μm.

[0296]

[0297] Comparative Example 2

[0298] Lithium nickel cobalt manganese aluminum oxide (NCMA, Li[Ni)) as the cathode active material 0.88 Co 0.07 Mn0.04 ]Al 0.01 O2) 95.7g, 1g of carbon black as a conductive agent, 2.3g of polytetrafluoroethylene (PTFE) as a binder, and 1g of a polypropylene copolymer (Woosung Chemical, SP3789) (Tm 165℃, Melt Index 3g / 10min (measured under 230℃, 2.16kg conditions)) containing a maleic anhydride-derived functional group as a modified polyolefin were placed in a blender and mixed at 10,000 rpm for 1 minute to prepare a mixture, and the resultant was placed in a kneader. At this time, the average particle diameter (D50) of the polypropylene copolymer containing a maleic anhydride-derived functional group as a modified polyolefin was 450㎛.

[0299] The temperature of the kneader was stabilized at 180°C, and the mixture was placed in a pressurized kneader and operated at a speed of 40 rpm for 10 minutes under a pressure of about 1.1 atm to obtain a mixture lump. The mixture lump was placed in a blender, ground at 10,000 rpm for 30 seconds, and classified with a sieve having pores of 1 mm in size to obtain a mixed powder for electrodes. Thereafter, the prepared mixed powder for electrodes was placed in a wrap calender (roll diameter: 160 mm, roll temperature: 100°C) to produce a film, and then calendered twice repeatedly to finally produce an electrode film. Two sheets of the electrode films thus prepared were placed on both sides of aluminum foil (thickness: 19 μm) not coated with a primer layer, and laminated through a compression roll maintained at 150°C to produce an electrode (positive electrode).

[0300] The total thickness of the final manufactured electrode was 175 μm, and the thickness of the active material layer formed on one side of the active material layers provided on both sides of the current collector was 78 μm.

[0301]

[0302] Comparative Example 3

[0303] An electrode was manufactured in the same manner as in Example 1, except that the temperature of the kneader was controlled at 180°C.

[0304] The total thickness of the final manufactured electrode was 171 μm, and the thickness of the active material layer formed on one side of the active material layers provided on both sides of the current collector was 76 μm.

[0305]

[0306] Melting point evaluation of modified polyolefins

[0307] The melting points of the modified polyolefins used in Examples 1 to 3 and Comparative Examples 1 to 3 were measured using a Differential Scanning Calorimeter (DSC, Device Name: DSC 2920, Manufacturer: TA Instrument). Specifically, the modified polyolefin sample to be measured was placed in the differential scanning calorimeter, heated to 220°C, maintained at that temperature for 5 minutes, cooled to 20°C, and then increased again in temperature, with the temperature rising and falling rates each being controlled to 10°C / min.

[0308]

[0309] Performance Evaluation

[0310] The following evaluation was conducted on the positive electrodes manufactured in Examples 1 to 3 and Comparative Examples 1 to 3, and the results are shown in Table 1.

[0311]

[0312] Evaluation of initial adhesion (adhesion before immersion in electrolyte)

[0313] Double-sided tape was attached to a slide glass, and anode samples manufactured in Examples 1 to 3 and Comparative Examples 1 to 3, each of which was punched out to a size of 20 mm X 100 mm, were placed on top of it, and a 2 kg roller was used to reciprocate 10 times to adhere them, and then a laminating machine with a gap of 5 mm and a speed of 5 mpm was used to remove air bubbles. Then, the adhesive strength was measured by the force required to peel off the slide glass by pulling it at 100 mm / min using a UTM (TA) machine. At this time, the measurement angle between the slide glass and the electrode was 90°.

[0314]

[0315] Adhesion after electrolyte immersion

[0316] A liquid electrolyte was prepared in which 1 M LiPF6 was dissolved in a solvent containing ethylene carbonate, dimethylene carbonate, and diethyl carbonate in a 1:2:1 (volume ratio), and the positive electrodes manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 were immersed in it for one week. After immersing in the electrolyte, the positive electrodes were taken out, washed with a DMC solution, dried, and a positive electrode sample punched out to 20 mm X 100 mm was placed on them, and bonded by reciprocating 10 times with a 2 kg roller, and then, after removing air bubbles using a laminating machine with a gap of 5 mm and a speed of 5 mpm, the adhesive strength after immersion in the electrolyte was measured by peeling the electrode from a slide glass at a pull of 100 mm / min using a UTM (TA) device. At this time, the measurement angle between the slide glass and the electrode was 90°.

[0317]

[0318] Initial interface resistance (resistance before electrolyte immersion)

[0319] The interfacial resistance was calculated by applying a current of 100 μA to the anodes manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 using the MP (Multi Probe) resistance measurement method, and measuring the resistance value between the dry electrode film and the electrode layer using the potential difference measured between multiple probes.

[0320]

[0321] Interfacial resistance after electrolyte immersion

[0322] A liquid electrolyte was prepared in which 1 M LiPF6 was dissolved in a solvent containing ethylene carbonate, dimethylene carbonate, and diethyl carbonate in a 1:2:1 (volume ratio) mixture, and the positive electrodes manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 were immersed in the electrolyte for one week. After immersing the positive electrode in the electrolyte, the interface resistance of the positive electrode taken out was calculated by applying a current of 100 μA using the MP (Multi Probe) resistance measurement method and measuring the resistance value between the dry electrode film and the electrode layer as the potential difference measured between multiple probes.

[0323]

[0324] Evaluation of the breaking strength per unit width of the electrode layer (electrode film)

[0325] The positive electrode films (electrode films) manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 were cut into 1 cm X 5 cm to prepare samples, and the samples were pulled at a speed of 5 cm / min using UTM (Zwick) to measure stress and strain, and the maximum stress value just before fracture was measured as tensile strength (kgf / cm 2 , or MPa), and the tensile strength at this time was multiplied by the thickness of the electrode film to calculate the breaking strength per unit width of the electrode layer (electrode film).

[0326]

[0327] Appearance evaluation

[0328] (1) Number of unusual areas

[0329] The number of heterochromatic regions per unit area (square meter) on the surface of the electrode was evaluated as follows.

[0330] Using a vision camera inspection system (product of Inteck Plus), light was irradiated to the entire surface of the electrode in the width direction at 30 degrees with an LED light source, and the vision camera detected the light (reflected light) irradiated from the LED light source and reflected from the electrode surface, recorded the intensity of the reflected light in pixel units through an image sensor, and analyzed the reflection characteristics of the electrode surface by processing the data collected from the vision camera to identify an area with a gray value difference (△GV) greater than 20 compared to the background, and if the major axis length of the horizontal cross-section of the identified area was 1.5 mm or longer, it was determined to be a heterochromatic area.

[0331] The gray value difference (△GV) is defined by the following equation.

[0332] Gray value difference (△GV) = |background GV - heterochromatic region GV|

[0333] At this time, the criteria for good and bad electrode appearance are as follows.

[0334] Good: Number of heterochromatic areas is 5 / m 2 below

[0335] Defective: Number of heterochromatic areas is 6 / m 2 more

[0336]

[0337] (2) Appearance observation

[0338] The photographs observing the surface of the anode manufactured in Example 1 and Comparative Example 1 are shown in FIGS. 5 and 6, respectively.

[0339] Referring to FIGS. 5 and 6, the surface of the anode of Example 1 exhibits a very good appearance (FIG. 5), but in the case of the anode of Comparative Example 1, numerous appearance defects were observed on the surface (FIG. 6).

[0340] Adhesion (gf / 2cm) Adhesion after immersion in electrolyte (gf / 2cm) Initial interfacial resistance (Ωcm) Interfacial resistance after immersion in electrolyte (Ωcm) Appearance (Number of heterochromatic areas on the electrode surface (ea / m) 2)) Breaking strength per unit width (N / cm)Example 11952020.210.42Good (0)0.79Example 21841960.230.51Good (3)0.80Example 31901980.190.40Good (0)1.16Comparative Example 11251300.250.55Poor (bundle, 50 or more)1.05Comparative Example 275840.290.59Poor (7)0.52(NG)Comparative Example 31751840.220.46Good (0)0.38(NG)

[0341]

[0342] Referring to Table 1, the electrodes manufactured in Examples 1 to 3 including modified polyethylene had a much smaller number of heterochromatic regions on the electrode surface compared to the electrodes of Comparative Examples 1 and 3, resulting in excellent uniformity of the electrode surface and significantly improved appearance characteristics. At the same time, the breaking strength per unit width was secured at 0.6 N / cm or more, so that the roll-to-roll process could proceed without breaking, and it was found that both the pre- and post-adhesive strengths after immersion in the electrolyte were remarkable. On the other hand, the electrode of Comparative Example 1 had satisfactory breaking strength but significantly poor appearance characteristics, and Comparative Examples 2 and 3 showed very poor results in both the breaking strength and appearance characteristics of the electrodes.

Claims

1. An electrode comprising an electrode current collector; and an electrode layer positioned on the electrode current collector and including an active material, a conductive material, and a binder; The above binder comprises a fluorinated polymer and a modified polyolefin, The surface of the above electrode is 5 / m 2 It has the following unusual areas: The above modified polyolefin contains at least one functional group among a carboxylic anhydride derived functional group and a carboxylic acid derived functional group, An electrode characterized in that the breaking strength per unit width of the electrode layer is 0.6 N / cm or more.

2. In paragraph 1, The surface of the above electrode is 0 to 3 / m 2 An electrode characterized by having the following heterochromatic regions:

3. In paragraph 1, An electrode characterized in that the breaking strength per unit width of the electrode layer is 0.6 N / cm to 3 N / cm.

4. In paragraph 1, An electrode characterized in that the modified polyolefin is derived from modified polyolefin particles having an average particle diameter of 0.5 mm or less.

5. In paragraph 1, An electrode characterized in that the content of the modified polyolefin is 2 to 40 parts by weight based on 100 parts by weight of the binder.

6. In paragraph 1, An electrode characterized in that the melting point of the modified polypolyolefin is 140°C or lower.

7. In paragraph 1, An electrode, characterized in that the modified polyolefin comprises at least one of modified polyethylene and modified polypropylene.

8. In paragraph 1, The above olefin comprises at least one of ethylene and propylene, At least one functional group among the above carboxylic acid anhydride derived functional group and the carboxylic acid derived functional group is selected from the group consisting of maleic anhydride, glutaric anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic monoanhydride, pyromellitic dianhydride, 1,8-naphthalenedicarboxylic acid anhydride, 2,3-naphthalenedicarboxylic acid anhydride, 1,4,5,8-naphthalenetetracarboxylic acid monoanhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid monoanhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, maleic acid, glutaric acid, phthalic acid, trimellitic acid, pyromellitic acid, 1,8-naphthalenedicarboxylic acid, An electrode characterized by being derived from 2,3-naphthalenedicarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, or two or more thereof.

9. In paragraph 1, An electrode characterized in that the modified polyolefin is modified polyethylene.

10. In paragraph 1, An electrode characterized in that the modified polyolefin is at least one of polyethylene containing a maleic anhydride-derived functional group and polypropylene containing a maleic anhydride-derived functional group.

11. In paragraph 1, An electrode characterized in that the content of at least one functional group among a carboxylic anhydride-derived functional group and a carboxylic acid-derived functional group in the modified polyolefin is 0.5 to 20 mol%.

12. In paragraph 1, An electrode characterized in that the binder is fiberized to bind the active material and the conductive material.

13. In paragraph 1, An electrode characterized in that the binder contains polytetrafluoroethylene (PTFE).

14. In paragraph 1, An electrode characterized in that the content of the active material is 80 to 98 parts by weight, the content of the conductive material is 0.5 to 10 parts by weight, the content of the fluorinated polymer is 0.5 to 5 parts by weight, and the content of the modified polyolefin is 0.02 to 3.3 parts by weight.

15. In paragraph 1, An electrode characterized in that the electrode current collector does not include a conductive primer layer on at least one surface.

16. In paragraph 1, An electrode characterized in that the electrode layer is derived from a film for a dry electrode.

17. A step of preparing a mixture including an active material, a conductive material, and a binder, wherein the binder includes a fluorinated polymer and a modified polyolefin; A step of kneading the mixture at a temperature ranging from 70°C to 170°C and under a pressure higher than normal pressure to produce a mixture lump; A step of crushing the above mixture lump to obtain a mixed powder for electrode; A step of forming an electrode film by putting the above electrode-use mixed powder between a plurality of rolls and performing calendaring processing; and A method for manufacturing an electrode according to claim 1, characterized by including a step of laminating the electrode film onto a metal current collector.

18. In paragraph 17, A method for manufacturing an electrode, characterized in that the modified polyolefin has an average particle diameter of 0.5 mm or less.

19. In Article 17, A method for manufacturing an electrode, characterized in that the step of manufacturing a mixture lump by mixing is performed in a kneader under a pressure higher than atmospheric pressure.

20. A secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, characterized in that at least one of the positive electrode and the negative electrode is an electrode according to any one of claims 1 to 16.

21. An energy storage device including a secondary battery according to Article 20 as a unit battery.

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