Electrodes and methods for manufacturing electrodes

Abstract

The present application provides an electrode and a manufacturing method thereof that can improve the impregnation of an electrolyte solution, thereby improving performance without compromising the safety of the battery, improve performance such as an increase in battery life by adjusting the width and depth of the recessed shape, increase the surface area by using a recessed shape having an appropriate width, and reduce the resistance of the electrode by reducing the thickness of the electrode.

Description

[Technical Field]

[0001] Mutual citation with related applications This application claims priority rights based on Republic of Korea Patent Application No. 10-2021-0113140 dated August 26, 2021, and Republic of Korea Patent Application No. 10-2022-0107196 dated August 25, 2022, and all content disclosed in the documents of the relevant Korean patent applications is incorporated herein by reference.

[0002] Technical field This application relates to an electrode having an incised shape and a method for manufacturing the electrode having the incised shape. [Background technology]

[0003] As technological development and demand for mobile devices and electric vehicles increase, so does the demand for rechargeable batteries as an energy source, and as a result, much research is underway to meet diverse requirements. Nickel-metal hydride batteries, lithium batteries, and lithium-ion batteries are used as rechargeable batteries, with lithium-ion batteries being the most representative.

[0004] Generally, a secondary battery includes an electrode assembly in which a positive electrode and a negative electrode, each coated with a positive electrode active material and a negative electrode active material respectively, are arranged with a separator (separation membrane) in between, and an outer casing material that seals and houses the electrode assembly together with an electrolyte.

[0005] Here, the electrolyte is a medium for ion movement, and when the electrolyte is injected into the electrode assembly, it enters the space between the positive electrode, negative electrode, and separator by capillary force. If the electrolyte is not completely impregnated between the positive electrode, negative electrode, and separator, the reaction between the electrodes will not be smooth, the resistance will increase, and the output characteristics and battery capacity will rapidly decrease. This will not only result in a decrease in battery performance and a shortened lifespan, but the high resistance may also cause battery degradation or even explosion.

[0006] In particular, high-loading technology, which involves changing the composition of the active material or increasing the amount of active material, has recently been applied to improve the energy storage capacity of secondary batteries. However, as mentioned above, when high-loading technology is applied, the battery performance is not properly realized due to incomplete impregnation of the electrolyte.

[0007] Furthermore, in order to ensure safety and battery performance in lithium-ion batteries, the negative electrode is formed to have a larger surface area than the positive electrode, thereby further increasing the discharge capacity per unit area of ​​the active material. However, in the case of a negative electrode with an incision, the amount of negative electrode active material facing the negative electrode portion decreases, which may reverse the discharge capacity per unit area. In this case, the ratio of the capacity per unit area of ​​the negative electrode to the positive electrode (the so-called NP ratio) decreases, which leads to the problem of lithium metal deposition.

[0008] In contrast, Patent Document 1 includes a current collector and an active material layer, wherein the active material layer comprises a pattern having multiple line shapes formed at a certain depth from the surface and spaced apart from each other, and the ratio of the depth to the width of the pattern (pattern depth / pattern width) is 0.2 to 1.0, thereby improving electrolyte impregnation. However, when the ratio of the depth to the width of the pattern is within the aforementioned range, there is a problem that the charging time increases. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Korean Published Patent Publication No. 10-2016-0116969 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] This application provides an electrode and a method for manufacturing the same, which can improve the performance of the battery by improving the impregnation of the electrolyte, thereby not compromising the safety of the battery.

[0011] Furthermore, this application provides an electrode and a method for manufacturing the same that can improve performance, such as increasing battery life, by adjusting the width and depth of the engraved shape.

[0012] Furthermore, this application provides an electrode and a method for manufacturing the same, which can improve the impregnation of the electrolyte by increasing the surface area with an incised shape having an appropriate width, thereby reducing the resistance of the electrode by reducing its thickness. [Means for solving the problem]

[0013] Among the physical properties mentioned in this application, those whose results are affected by the measurement temperature and / or measurement pressure are those measured under normal temperature and / or normal pressure conditions unless otherwise specified. Furthermore, among the physical properties mentioned in this application, those whose results are affected by the measurement humidity are those measured under normal humidity conditions unless otherwise specified.

[0014] As used in this application, "room temperature" refers to the natural temperature without heating or cooling. For example, "room temperature" could be any temperature within the range of 10°C to 30°C, and could mean a temperature of approximately 23°C or 25°C. Unless otherwise specified, the unit of temperature used in this application is Celsius (°C).

[0015] As used in this application, "atmospheric pressure" refers to the natural pressure that is not pressurized or depressurized. For example, the aforementioned atmospheric pressure may mean approximately 1 atmosphere, which is the level of normal atmospheric pressure.

[0016] As used in this application, "normal humidity" refers to the natural humidity that is not specifically regulated under normal temperature and / or atmospheric pressure conditions. For example, "normal humidity" may mean a range of approximately 20RH% to 80RH% or 40RH% to 60RH% under normal temperature and / or atmospheric pressure conditions, and the unit RH% (Relative Humidity%) used herein represents the current amount of water vapor as a percentage, with the maximum amount of water vapor that can be contained at a particular temperature being set to 100.

[0017] Unless otherwise specified, the thickness of any layer used in this application may refer to that value if it is constant within the measurement range, or it may refer to the average thickness if it is not constant within the measurement range.

[0018] In this application, π refers to the ratio of a circle's circumference to its diameter (pi), which can be approximated and calculated using 3.1415.

[0019] Figure 1 is a drawing showing an electrode 1 according to an example of this application. The electrode 1 according to this example of this application may include a current collector 10 and an active material layer 20 formed on at least one surface of the current collector 10.

[0020] In one example of this application, the electrode 1 may have the active material layer 20 formed only on one surface of the current collector 10, while in other examples, the active material layer 20 may be formed on both sides of the current collector 10.

[0021] The current collector 10 of the electrode 1 in this application may be a positive electrode current collector or a negative electrode current collector.

[0022] The positive electrode current collector is not particularly limited in type, size, and shape, as long as it is conductive without inducing chemical changes in the secondary battery. Examples of materials that can be used as the positive electrode current collector include stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc. The adhesion between the positive electrode current collector and the positive electrode active material can be enhanced by forming fine irregularities on the surface of the positive electrode current collector, and various forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics are possible. Furthermore, the positive electrode current collector can have a thickness of 3 μm to 500 μm.

[0023] The negative electrode current collector is not particularly limited in type, size, and shape, as long as it is conductive without inducing chemical changes in the secondary battery. Examples of materials that can be used as the negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy. Also, similar to the positive electrode current collector, fine irregularities can be formed on the surface to strengthen the bonding force with the negative electrode active material, and it can be used in a variety of forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric. The negative electrode current collector can have a thickness of 3 μm to 500 μm.

[0024] The active material layer 20 of the electrode 1 in this application may be a positive electrode active material layer or a negative electrode active material layer. The active material layer 20 may include an electrode active material and a binder. The active material layer 20 may mean a layer in which an active material layer forming slurry is applied on the current collector 10, a layer in which the solvent has been removed by drying, or a layer formed by a drying and rolling process.

[0025] The electrode active material contained in the active material layer 20 is not particularly limited in terms of its specific type, and a material that normally forms a positive or negative electrode can be used.

[0026] For example, when the active material layer 20 is a positive electrode active material layer, the electrode active material is not particularly limited, but for example, layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0 ≤ c1 ≤ 0.33), LiMnO3, LiMn2O3, or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, or Cu2V2O7; chemical formula LiNi 1-c2 M c2 Ni-site type lithium nickel oxide represented as O2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01 ≤ c2 ≤ 0.3); chemical formula LiMn 2-c3 M c3 Lithium manganese composite oxides represented as O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, satisfying 0.01 ≤ c3 ≤ 0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); examples include, but are not limited to, lithium nickel cobalt manganese (NCM) composite oxides, lithium nickel cobalt manganese aluminum (NCMA) composite oxides, and LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions.

[0027] When the active material layer 20 is a negative electrode active material layer, the electrode active material may be, for example, a compound capable of reversible intercalation and deintercalation of lithium. Specific examples include carbonaceous materials such as graphite (artificial graphite, natural graphite, or graphitized carbon fiber) or amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. βExamples include metal oxides that can be doped and dedoped with lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites, and one or more mixtures of these may be used. A metallic lithium thin film may also be used as the negative electrode active material. Low-crystallinity carbon and high-crystallinity carbon may be used as the carbon material. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0028] From the viewpoint of capacity, the electrode active material preferably contains graphite (such as artificial graphite, natural graphite, or a combination thereof), and the active material layer 20 may be a negative electrode active material layer from the viewpoint of safety.

[0029] The ratio of electrode active material within the active material layer may be approximately 80% or more by weight, 81% or more by weight, 82% or more by weight, 83% or more by weight, 84% or more by weight, 85% or more by weight, 86% or more by weight, 87% or more by weight, or 88% or more by weight, or 99% or less by weight or 98% or less by weight.

[0030] The binder contained in the active material layer 20 is not particularly limited in terms of its specific type, and any substance that typically serves to improve adhesion between electrode active materials and adhesion between the electrode active materials and the current collector can be used.

[0031] Examples of the binders are not particularly limited and include, for example, polyvinylidene fluoride (PVDF), polyvinyl alcohol, styrene butadiene rubber (SBR), polyethylene oxide, carboxymethyl cellulose (CMC), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose. One or more compounds may be selected and used from the group consisting of sucrose, pullulan, polymethyl methacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyarylate, and low molecular weight compounds with a molecular weight of 10,000 g / mol or less.

[0032] The binder may be contained in an amount of 0.1 part by weight or more, 0.2 part by weight or more, 0.3 part by weight or more, 0.4 part by weight or more, 0.5 part by weight or more, 0.6 part by weight or more, 0.7 part by weight or more, 0.8 part by weight or more, 0.9 part by weight or more, or 1 part by weight or more, or 10 parts by weight or less, 9.5 parts by weight or less, 9 parts by weight or less, 8.5 parts by weight or less, 8 parts by weight or less, 7.5 parts by weight or less, 7 parts by weight or less, 6.5 parts by weight or less, 6 parts by weight or less, 5.5 parts by weight or less, 5 parts by weight or less, 4.5 parts by weight or less, 4 parts by weight or less, 3.5 parts by weight or less, 3 parts by weight or less, 2.5 parts by weight or less, or 2 parts by weight or less, based on 100 parts by weight of the electrode active material, in terms of improving the adhesion to the electrode active material layer described above and ensuring the desired viscosity.

[0033] Also, it may be advantageous to use a binder having a solubility parameter within the range described below for forming an appropriate network region among the components within the active material layer 20.

[0034] From the viewpoint of improving the impregnation property of the electrolyte, it may be necessary to use a binder having a solubility parameter of about 10 to 30 MPa 1 / 2 or so. The solubility parameter is, in other examples, 11 MPa 1 / 2 or more, 12 MPa 1 / 2 or more, 13 MPa 1 / 2 or more, 14 MPa 1 / 2 or more, 15 MPa 1 / 2 or more, or 16 MPa 1 / 2 or more, or 28 MPa 1 / 2 or less, 26 MPa 1 / 2 or less, 24 MPa 1 / 2 or less, 22 MPa 1 / 2 or less, 20 MPa 1 / 2 or less, or 18 MPa 1 / 2The following are possible. The solubility parameter of such a binder is known as the Hansen solubility parameter and can be confirmed through literature (e.g., Yanlong Luo et al., 2017, J.Phys.Chem.C 2017, 121, 10163-10173, DOI:10.1021 / acs.jpcc.7b01583, etc.). For example, a type of binder of the aforementioned type having the aforementioned solubility parameter may be selected.

[0035] The active material layer 20 may additionally contain a conductive material. The conductive material is not particularly limited as long as it is conductive without inducing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, kechen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes (CNTs); metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0036] The conductive material may be included in an amount of 0.1 to 5 parts by weight or 0.5 to 2 parts by weight relative to 100 parts by weight of the electrode active material, but is not limited thereto. Methods for determining the content of the conductive material at an appropriate level, taking into consideration the battery's cycle life, etc., are well known.

[0037] The thickness of the active material layer 20 can be 50 μm to 200 μm. In particular, even when using high loading technology, which has recently been applied to improve the energy storage capacity of secondary batteries, the electrode 1 according to this example of the present application can improve the impregnation of the electrolyte by the engraved shape 21 described below, thereby ensuring excellent battery performance.

[0038] An incised shape 21 may be present in the active material layer 20 of the electrode 1 according to an example of this application. The incised shape 21 may be formed at a certain depth from the surface of the active material layer 20.

[0039] The ratio (Vp / V) of the volume Vp of the engraved shape 21 of the electrode 1 according to an example of this application to the volume V of the active material layer 20 can satisfy the following formula 1.

[0040] [Formula 1] a ≤ Vp / V × 100 ≤ b

[0041] In Equation 1, Vp is the volume of the incised shape, and V is the volume of the active material layer. Also, a can be 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, or 0.2, and b can be 0.6, 0.59, 0.58, 0.57, 0.56, 0.55, 0.54, 0.53, 0.52, 0.51, or 0.5.

[0042] If the ratio (Vp / V) of the volume Vp of the engraved shape 21 of the electrode 1 according to an example of this application to the volume V of the active material layer 20 satisfies formula 1, the impregnation of the electrolyte into the active material layer 20 can be improved, thereby enabling improvements in performance such as increased battery life and reduced resistance.

[0043] Furthermore, if the ratio (Vp / V) of the volume Vp of the engraved shape 21 of the electrode 1 according to an example of this application to the volume V of the active material layer 20 satisfies formula 1, then the impregnation rate V and the size of impregnation (S) according to formula 2 described later can be determined. p ) and impregnation time (t p ) can reach a level that achieves the purpose of this application. In other words, when the engraved shape is elliptical, the major axis (L maj ) and minor axis (L min ) ratio (L maj / L min ) can reach a level that achieves the objectives of this application.

[0044] Figure 2 is a perspective view of an electrode 1 according to an example of this application. The active material layer 20 may be formed on at least one surface of the current collector 10, and has a width L T It may take the form of a hexahedron with width W and thickness T. In this case, the volume V of the active material layer 20 is L T The volume is L × W × T. Furthermore, an incised shape 21, which is an incised rectangular hexahedron with width L, width W, and depth D, may be formed on the active material layer 20. In this case, the volume Vp of the incised shape 21 is L × W × D. While Figure 2 illustrates a method for measuring the ratio of the volume Vp of the incised shape 21 to the volume V of the active material layer 20, the method is not limited to this, and the Vp / V ratio can be measured using volume measurement methods or programs commonly used in this industry, even if the shape is not a rectangular hexahedron. The volume V of the active material layer 20 may include the volume Vp of the incised shape 21.

[0045] In one example of this application, the width L of the engraved shape 21 formed on the electrode 1 may be 100 μm or more. In another example, the width L of the engraved shape 21 may be 150 μm or more, 200 μm or more, 250 μm or more, 300 μm or more, 350 μm or more, 400 μm or more, 450 μm or more, or 500 μm or more. In yet another example, the upper limit of the width L of the engraved shape 21 is not particularly limited, but may be, for example, 2,000 μm or less, 1,800 μm or less, 1,600 μm or less, 1,400 μm or less, or 1,200 μm or less. In yet another example, the width L of the engraved shape 21 may be within the range formed by appropriately selecting the upper and lower limits mentioned above.

[0046] Furthermore, the term width L of the engraved shape 21, as used in this application, may mean the average distance of the shortest distances between the two ends of two lines formed on the surface of the active material layer 20. For example, referring to the engraved shape 21a in Figure 3, two lines (22a and 22b) are formed on the surface of the active material layer 20, and the average distance of the shortest distances between the two lines (22a and 22b) may be the width L of the engraved shape 21a. Here, the shortest distance between the two ends of the two lines may mean the distance L1 between any point a1 on one line 22a and any point a2 on the other line 22b that is the shortest distance away. In other words, the average of the shortest distances between the two ends of the two lines formed on the surface of the active material layer 20 in the width direction of the engraved shape 21 may be the width L of the engraved shape 21.

[0047] When the width L of the engraved shape 21 formed on the electrode 1 according to an example of this application is in the range of 100 to 800 μm, the ratio of the width L to the depth D of the engraved shape 21 (D / L) may be 0.005 or more, 0.075 or more, 0.01 or more, 0.0125 or more, 0.015 or more, 0.0175 or more, or 0.02 or more, and in other examples, the ratio of the width L to the depth D of the engraved shape 21 (D / L) may be 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, or 0.1 or less. The ratio of the width L to the depth D of the engraved shape 21 (D / L) may be within the range formed by appropriately selecting the upper and lower limits. Furthermore, as another example, the width L of the engraved shape 21 may be in the range of 150 to 750 μm, 200 to 700 μm, 250 to 650 μm, 300 to 600 μm, or 350 to 550 μm. When the ratio of the width L to the depth D of the engraved shape 21 (D / L) satisfies the above range, lithium deposition can be prevented and battery performance such as increased lifespan can be improved.

[0048] As used in this application, the term "depth" may mean a constant value within the measurement range, or it may mean the depth of the deepest point from the surface if it is not constant within the measurement range.

[0049] When the width L of the engraved shape 21 formed on the electrode 1 according to one example of this application exceeds 800 μm, the ratio of the width L to the depth D of the engraved shape 21 (D / L) may be 0.005 or more, 0.0055 or more, 0.006 or more, 0.0065 or more, 0.007 or more, 0.0075 or more, 0.008 or more, 0.0085 or more, 0.009 or more, or 0.0095 or more. In other examples, the ratio of the width L to the depth D of the engraved shape 21 (D / L) may be within the range of 0.025 or less, 0.0225 or less, 0.02 or less, 0.0175 or less, 0.015 or less, or 0.0125 or less. The ratio of the width L to the depth D of the engraved shape 21 (D / L) may be within the range formed by appropriately selecting the upper and lower limits mentioned above. Furthermore, as another example, the width L of the engraved shape 21 may be in the range of 850 to 2,000 μm, 900 to 1,900 μm, 925 to 1,800 μm, 950 to 1,700 μm, or 975 to 1,500 μm. When the ratio of the width L to the depth D of the engraved shape 21 (D / L) satisfies the above range, lithium deposition can be prevented and battery performance such as increased lifespan can be improved.

[0050] The engraved shape 21 formed on the electrode 1 according to an example of this application only needs to satisfy the aforementioned range in terms of the Vp / V ratio and the depth D / width L ratio, and there are no particular restrictions on the width as long as it does not extend beyond the active material layer 20. For example, referring to Figure 3, the electrode 1 according to an example of this application may be provided with an engraved shape 21b having a width L, a width W', and a depth D, which are smaller than the width W of the active material layer 20. Furthermore, the external form of the engraved shape 21b is not particularly limited, as long as the aforementioned range is satisfied in terms of the Vp / V ratio and the depth D / width L ratio, which are

[0051] In one example of this application, the electrode 1 may have a single or multiple incised shapes 21 formed on the surface of the active material layer 20. Referring to Figure 2, the incised shape 21 may be formed as a single shape on the surface of the active material layer 20. Referring to Figure 4, the incised shapes 21 may be formed as multiple shapes on the surface of the active material layer 20. When multiple incised shapes 21 are formed on the surface of the active material layer 20, each incised shape 21 can have an independent form (external or internal). Furthermore, they may be formed in the same manner or in different manners.

[0052] Furthermore, if multiple incised shapes 21 are formed on the electrode 1 according to an example of this application, they may be formed intersecting each other or not intersecting each other. In addition, the spacing between adjacent incised shapes 21 may be 10 μm or more, 50 μm or more, 100 μm or more, 105 μm or more, 110 μm or more, 115 μm or more, 120 μm or more, 125 μm or more, 130 μm or more, 135 μm or more, 140 μm or more, 145 μm or more, 150 μm or more, 155 μm or more, or 160 μm or more, and in other examples it may be 200 μm or less, 195 μm or less, 190 μm or less, 185 μm or less, 180 μm or less, 175 μm or less, or 170 μm or less. The spacing between the plurality of engraved shapes 21 can be within a range formed by appropriately selecting the upper and lower limits mentioned above, and if this is satisfied, the impregnation of the electrolyte into the active material layer 20 can be improved while preventing a decrease in the storage capacity of the active material. The spacing between adjacent engraved shapes 21 in the plurality of engraved shapes 21 can mean the shortest distance between opposing outermost lines, as shown by the spacing S in Figure 3.

[0053] In the example of the electrode 1 according to this application, if a plurality of incised shapes 21 are formed on the surface of the active material layer 20, then in formula 1, Vp may represent the total volume of the plurality of incised shapes 21.

[0054] When multiple incised shapes 21 are formed on the surface of the active material layer 20, if the ratio of the total volume Vp of the incised shapes 21 to the volume V of the active material layer 20 (Vp / V) satisfies the aforementioned formula 1, the impregnation of the active material layer 20 with the electrolyte can be improved, which can lead to improved performance such as increased battery life and reduced resistance.

[0055] The internal shape of the engraved shape 21 of the electrode 1 according to this application is not particularly limited. Figure 4 is a cross-sectional view showing an example of the internal shape of the engraved shape 21, and this is merely an example and not a limitation. For example, referring to Figure 4, there is an engraved shape 21c that narrows in width towards the interior, an engraved shape 21d with steps, and an engraved shape 21e with irregularities U formed thereon.

[0056] The engraved shape 21 of the electrode 1 according to an example of this application may have one or more steps inside. The term "step" as used in this application may mean the difference in height between the first surface and the second surface. Specifically, the engraved shape 21 may have two or more steps inside and have a stepped structure, as shown in the engraved shape 21d of Figure 4. By forming steps inside the engraved shape 21 in this way, the surface area can be increased, thereby improving the impregnation of the electrolyte into the active material layer 20.

[0057] Furthermore, the engraved shape 21 of the electrode 1 according to one example of this application may have irregularities U on its inner bottom surface. Specifically, as shown in the engraved shape 21e of Figure 4, the inner bottom surface may have irregularities U with a predetermined pattern, or it may have irregular irregularities U. By forming irregularities U on the inner bottom surface of the engraved shape 21 in this way, the surface area can be increased, thereby improving the impregnation of the electrolyte into the active material layer 20.

[0058] In one example of this application, the depth D of the engraved shape 21 formed on the electrode 1 may be a ratio (D / T) of the thickness T of the active material layer 20 of 0.1 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, 0.19 or more, or 0.2 or more. In other examples, the ratio (D / T) of the depth D of the engraved shape 21 to the thickness T of the active material layer 20 may be 0.6 or less, 0.59 or less, 0.58 or less, 0.57 or less, 0.56 or less, 0.55 or less, 0.54 or less, 0.53 or less, 0.52 or less, 0.51 or less, or 0.5 or less. The ratio (D / T) of the depth D of the engraved shape 21 to the thickness T of the active material layer 20 may be within the range formed by appropriately selecting the upper and lower limits mentioned above.

[0059] Here, the thickness T of the active material layer 20 refers to the thickness of the active material layer 20 assuming that the engraved shape 21 is not formed. The thickness of the active material layer 20 used in this application may refer to the value if it is constant within the measurement range, or it may refer to the average thickness if it is not constant within the measurement range. Specifically, for an active material layer 20 formed on an arbitrary plane viewed from the side within the measurement range, the thickness can be defined as the vertical distance from a point on the plane to the surface of the active material layer 20. Here, if the vertical distance is constant within the measurement range, it becomes the thickness of the active material layer 20 itself, and if the vertical distance is different within the measurement range, the average thickness becomes the thickness of the active material layer 20. Furthermore, the average thickness can be calculated by dividing the line where the plane and the active material layer 20 are in contact within the measurement range into 10 equal parts at regular intervals, setting points formed at 10 equal divisions on the line, and taking the average of the vertical distances of the remaining points excluding the points at both ends. The above has described the thickness of the active material layer 20, but unless otherwise specified, the thickness of other configurations can also be described in the same way.

[0060] As used in this application, the term "constant" may mean exactly the same level, or it may mean substantially the same level with a predetermined error (a difference of 5% or less). The predetermined error may mean the percentage (%) obtained by dividing the absolute value of the value obtained by subtracting a specific measurement from the average value by the average value.

[0061] When the depth D of the engraved shape 21 is within the range described above relative to the thickness T of the active material layer 20, it is possible to improve the impregnation of the electrolyte while preventing a decrease in the energy density of the battery.

[0062] In this application, objects for which units of length are used (for example, thickness, depth, width, height, etc., and objects not included in this example may fall under this category if units of length are used) may be measured using a steel ruler or caliper, or using a precision mechanical device.

[0063] An engraved shape 21 formed on an electrode 1 according to an example of this application can be formed by laser irradiation. The engraved shape 21 can be formed by forming an active material layer 20 on at least one surface of a current collector 10 and then irradiating the surface of the active material layer 20 with a laser.

[0064] The aforementioned laser irradiation can form an engraved shape 21 on the electrode 1 according to an example of this application by adjusting the laser beam size. Here, the laser beam size can be changed through changes in the laser's optics and focusing position. The change in beam size through optics can be changed by the magnification of a collimating lens that prevents the beam from spreading and the magnification of an F-theta lens designed so that the beam that has passed through the laser scanner is focused on the same plane. This can also be achieved by appropriately adjusting the in-focus or out-focus plane of the laser beam.

[0065] Furthermore, the size of the laser beam can be varied depending on the wavelength and power output. The wavelength of the laser beam can be, for example, 300 to 2,000 nm, and specifically, a variety of wavelengths such as 1.06 μm, 532 nm, 355 nm, 266 nm, and 248 nm can be selected. The power output of the laser beam can be approximately 500 W, and is not particularly limited.

[0066] The aforementioned laser irradiation can be performed using IR lasers, excimer lasers, YAG lasers, carbon dioxide lasers, etc., but there are no particular restrictions on which lasers can be used as long as they are used in this industry.

[0067] Furthermore, the laser irradiation can be performed using a gaseous medium or a solid-state medium. The gaseous medium can be selected from He-Ne, carbon dioxide, Ar, and excimer lasers, and the solid-state medium can be selected from Nd:YAG, Nd:YVO4, and Ytterbium fiber.

[0068] Electrode 1 in this application, as an example, has an impregnation rate (V) of 1.5π mm as shown in Equation 2 below. 2 / s (start) or more, 1.525π mm 2 / s or more, 1.55πmm 2 / s or more, 1.575πmm 2 / s or more, 1.6πmm 2 / s or more, 1.625πmm 2 / s or more, 1.65πmm 2 / s or more, 1.675πmm 2 / s or more, 1.7πmm 2 / s or more, 1.725πmm 2 / s or more, 1.75πmm 2 / s or more, 1.775πmm 2 / s or more, 1.8πmm 2 / s or more, 1.825πmm 2 / s or more, 1.85πmm 2 / s or more, 1.875πmm 2 / s or more, 1.9πmm 2 / s or more, 1.925πmm 2 / s or more, 1.95πmm 2 / s or more, 1.975πmm 2 / s or more or 2πmm 2 It may be more than / s. In another example, electrode 1 according to an example of this application has a V of 9.5π mm according to the following formula 2. 2 / s or less, 9.25πmm 2 / s or less, 9πmm 2 / s or less, 8.75πmm 2 / s or less, 8.5πmm 2 / s or less, 8.25πmm 2 / s or less, 8πmm 2 / s or less or 7.75πmm 2 It may be less than or equal to / s. The V of electrode 1 may be within a range formed by appropriately selecting the upper and lower limits mentioned above.

[0069] [Formula 2] V=S p / t p

[0070] In equation 2, S p This is the area of ​​the propylene carbonate (propylene carbonate, PC) impregnation region, which was confirmed by dropping 1 μl of propylene carbonate (propylene carbonate, PC) onto the incised shape of the electrode at 25°C. p This is the time required from the time of dropping until impregnation. Specifically, the impregnation rate and S are determined by the physical property measurement method described later. p and t p It is possible to find this.

[0071] The impregnation region refers to a wetting region in a planar form observed from the point where the propylene carbonate (PC) was dropped, in the direction of the surface it was dropped onto. Specifically, referring to Figure 2, the impregnation region appears as a planar form when observed from the point where the propylene carbonate (PC) was dropped, in the direction of the surface it was dropped onto in the incised shape 21, and this planar form can represent the wetting region of the propylene carbonate.

[0072] Furthermore, the shape of the impregnation area can be diverse, and may be, for example, a circle, an ellipse, or a polygon with a curved part.

[0073] Said t p This refers to the time it takes to complete the impregnation while maintaining the temperature after dripping. The completion of impregnation can be determined as the point at which the area onto which the propylene carbonate (PC) has been dripped is wet enough that the propylene carbonate (PC) does not stick to the hand when touched.

[0074] Furthermore, the dropping can be performed on the central point in the width direction of the incised shape 21, and the propylene carbonate (PC) can be dropped naturally using a dropper at a height of approximately 3 to 5 cm away from the surface on which the propylene carbonate (PC) is dropped.

[0075] When the impregnation rate V of electrode 1 according to formula 2 in an example of this application is within the range described above, the impregnation of the electrolyte can be improved, thereby improving performance within a range that does not impair the safety of the battery.

[0076] Electrode 1 in one example of this application is S in formula 2 above. p (Area of ​​impregnation region) is 60π mm 2 Less than 59πmm 2 Below, 58πmm 2 Below, 57πmm 2 Below, 56πmm 2 Below: 55mm² or less or 54πmm 2 The following is possible. Also, in another example, electrode 1 according to an example of this application is S in formula 2 above. p 10πmm 2 More than 12πmm 2 Above 14πmm 2 More than 16πmm 2 Above 18πmm 2 More than 20πmm 2 More than 22πmm 2 More than 24πmm 2 More than 26πmm 2 Above 28πmm 2Above, 30π mm 2 Above, 32π mm 2 Above, 34π mm 2 Above, 36π mm 2 Above, 38π mm 2 Above or 40π mm 2 It can be above. The S of the electrode 1 p can be within the range formed by appropriately selecting the aforementioned upper and lower limits.

[0077] The electrode 1 according to an example of the present application has t in the formula 2 p (The time required until the impregnation is completed after dropping or the impregnation time) can be 25 seconds or less, 24 seconds or less, 23 seconds or less, 22 seconds or less, 21 seconds or less, or 20 seconds or less. In another example, the t p can be 1 second or more, 5 seconds or more, 7 seconds or more, 9 seconds or more, or 10 seconds or more. The t of the electrode 1 p can be within the range formed by appropriately selecting the aforementioned upper and lower limits. Also, the impregnation time can be measured in an environment of normal pressure and normal humidity (about 40 - 60 RH%) and where there is no wind.

[0078] When the electrode 1 according to an example of the present application satisfies the impregnation rate V according to the formula 2 within the aforementioned range, and S p and t p are within the aforementioned range, the impregnability of the electrolytic solution can be improved, and thereby the performance can be improved within the range that does not inhibit the safety of the battery.

[0079] The electrode 1 according to an example of the present application has an impregnation region of propylene carbonate (PC) in an elliptical form when 1 μl of propylene carbonate (PC) is dropped onto the negative etching shape of the electrode at 25°C. The ratio of the major axis (L maj ) to the minor axis (L min ) of the elliptical form (L maj / L min ) can be more than 1, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, or 1.5 or more. In another example, the ratio (L maj / L min) may be 8 or less, 7.75 or less, 7.5 or less, 7.25 or less, 7 or less, 6.75 or less, 6.5 or less, 6.25 or less, or 6 or less. The major axis (L) of the impregnation region which has an elliptical shape. maj ) and minor axis (L min ) ratio (L maj / L min ) may be within the range formed by appropriately selecting the aforementioned upper and lower limits.

[0080] An example of the electrode 1 in this application satisfies the impregnation rate V according to formula 2 within the range described above, and the major axis (L) of the impregnation region which has an elliptical shape. maj ) and minor axis (L min ) ratio (L maj / L min If the above conditions are met within the aforementioned range, lithium deposition can be prevented, and an excellent battery life can be ensured.

[0081] A method for manufacturing an electrode 1 according to an example of this application may include the step of forming an incised shape 21 on an active material layer 20 formed on at least one surface of a current collector 10. The method for manufacturing an electrode 1 according to an example of this application can refer to the features of the electrode 1 according to an example of this application described above.

[0082] Specifically, a method for manufacturing an electrode 1 according to an example of this application may include a step of coating at least one surface of a current collector 10 with an active material layer forming slurry capable of forming an active material layer 20.

[0083] Here, as mentioned above, the current collector 10 can be a positive electrode current collector or a negative electrode current collector, and examples are as described above. Furthermore, various methods such as slot die coating, slide coating, and curtain coating can be applied to the slurry for forming the active material layer.

[0084] Furthermore, the slurry for forming the active material layer may contain an electrode active material and a binder. The electrode active material and binder are as described above, and their content may be based on the solid content. In addition, the slurry for forming the active material layer may contain a conductive material and, if necessary, a solvent. The solvent is not particularly limited as long as it is used in the industry, and for example, water, isopropyl alcohol, N-methylpyrrolidone (NMP), and acetone can be used.

[0085] A method for manufacturing an electrode 1 according to an example of this application may include a step of drying an active material layer forming slurry coated on at least one surface of a current collector 10. The coated active material layer forming slurry may be dried through a drying step, and if it contains a solvent, the solvent may be removed. At this time, the drying temperature is not particularly limited but may be in the range of about 70 to 200°C.

[0086] A method for manufacturing the electrode 1 according to an example of this application may include a step of rolling after the drying step. The capacity density of the active material can be increased through the rolling step, thereby increasing the adhesion between the current collector 10 and the active material layer 20. The rolling step may be a step of compressing the dried slurry with a rolling member, and the rolling member can be a rolling roller or a rolling jig.

[0087] The pressure applied in the rolling process can be appropriately adjusted within the range of 0.1 MPa to 90 MPa, 0.1 MPa to 50 MPa, 0.1 MPa to 30 MPa, or 0.1 MPa to 10 MPa. The rolling process can also be carried out using a roll press, in which case the speed of the roll press can be 20 m / min to 60 m / min.

[0088] A method for manufacturing an electrode 1 according to an example of this application can form an active material layer 20 by performing at least one of the steps described above. The method for manufacturing the electrode 1 may also include a step of forming an incised shape 21. The incised shape 21 can be formed to a predetermined depth from the surface of the formed active material layer 20. Here, as described above, the incised shape 21 can be formed using laser irradiation.

[0089] When using the aforementioned laser irradiation, the pattern can be accurately and precisely realized, and energy is effectively irradiated to a narrow area, thus preventing thermal damage to the active material layer 20. Details related to the laser irradiation have been described above and will be omitted here.

[0090] Electrode 1 in this application, as an example, may be a positive or negative electrode. Furthermore, this application can provide an electrode assembly including the electrode 1. The electrode assembly may include a positive electrode, a negative electrode, and a separator, and specifically may include a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. The positive electrode or the negative electrode may be an electrode according to an example of this application.

[0091] The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. Any separator commonly used in the industry can be used without particular limitations, and it is especially preferable that it has low resistance to ion movement in the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as polyolefin polymers like ethylene polymer, propylene polymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, coated separators containing ceramic components or polymeric substances to ensure heat resistance or mechanical strength may be used, and can be selectively used in single-layer or multi-layer structures.

[0092] The electrolyte can be, but is not limited to, organic liquid electrolytes, inorganic liquid electrolytes, gel-type polymer electrolytes, or molten inorganic electrolytes commonly used in this industry. Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0093] The aforementioned organic solvent can be used without particular limitations as long as it can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the aforementioned organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include a double-bond oriented ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, the electrolyte performance can be shown to be excellent when the cyclic carbonate and the linear carbonate are mixed in a volume ratio of about 1:1 to about 1:9.

[0094] The lithium salt can be any compound capable of providing lithium ions for use in lithium secondary batteries, without any particular limitations. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively.

[0095] In addition to the electrolyte components, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphate, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidinone, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1% to 5% by weight relative to the total weight of the electrolyte.

[0096] Furthermore, this application can provide a secondary battery including the electrode assembly. Specifically, the secondary battery may be a lithium-ion battery.

[0097] Furthermore, the secondary battery can be applied to portable devices such as mobile phones, laptop computers, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs). [Effects of the Invention]

[0098] The electrode and its manufacturing method according to this application improve the impregnation of the electrolyte, thereby improving performance within a range that does not impair the safety of the battery.

[0099] Furthermore, the electrode and its manufacturing method according to this application can improve performance, such as increasing battery life, by adjusting the width and depth of the engraved shape.

[0100] Furthermore, the electrode and its manufacturing method according to this application can increase the surface area by creating an incised shape with an appropriate width, thereby improving the impregnation of the electrolyte, and can reduce the electrode's thickness, thereby decreasing its resistance. [Brief explanation of the drawing]

[0101] [Figure 1] This is a cross-sectional view showing an example of electrode 1 according to this application. [Figure 2] This is a perspective view of electrode 1 according to an example of this application. [Figure 3] This is a perspective view of electrode 1 according to an example of this application. [Figure 4] This is a cross-sectional view illustrating an example of the internal shape of an engraved shape 21 according to an example of this application. [Figure 5] This is a cross-sectional view illustrating an example of the internal shape of an engraved shape 21 according to an example of this application. [Figure 6] This shows an example of an engraved shape 21 according to one example of this application, scanned with a measuring device. [Figure 7] This shows the remaining life capacity of the monocells manufactured in the examples and comparative examples. [Modes for carrying out the invention]

[0102] The present invention will be described below through examples, but the scope of the present invention is not limited to what is presented below.

[0103] Example 1 (1) Manufacturing of electrodes The negative electrode was manufactured by coating one entire surface of a copper foil with a thickness of 8 μm with a negative electrode active material composition (slurry), followed by drying and rolling processes.

[0104] The aforementioned negative electrode active material composition was prepared by mixing a negative electrode active material (artificial graphite:natural graphite = 3:7 by weight ratio, A), a conductive material (Super C65, B), styrene-butadiene rubber (SBR, C), and carboxymethylcellulose (CMC, D) in a weight ratio of 96:1:2:1 (A:B:C:D), and dispersing them in a solvent (water). The solubility parameter of the SBR was 16.9 MPa. 1 / 2 These solubility parameters are of a certain degree and are the values ​​described in the literature (Yanlong Luo et al., 2017, J.Phys.Chem.C 2017, 121, 10163-10173, DOI:10.1021 / acs.jpcc.7b01583).

[0105] The negative electrode active material composition was coated onto the copper foil using a gap coating method, dried at approximately 230°C for about 90 seconds, and then rolled to form an active material layer 20 with a thickness of approximately 90 μm.

[0106] Next, a 500W nanosecond pulse laser (fiber) was used to form an incised shape 21 on the surface of the active material layer 20, which was in the form of lines as shown in Figure 5, with irregularities U on the inner bottom surface. The width L of the line shape was about 500 μm, and the depth D was about 10 μm.

[0107] (2) Manufacturing of mono-cell An electrode assembly was manufactured by interposing a separator between the positive electrode and the manufactured negative electrode, and this was then housed in a case. Subsequently, an electrolyte was injected into the case to manufacture a monocell. The electrolyte was ethyl acetate. RenA lithium non-aqueous electrolyte was used, consisting of a mixture of carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7 (EC:EMC), and containing 1M lithium salt (LiPF6). After injecting the electrolyte, a mono-cell was manufactured by sealing the solution.

[0108] Example 2 The negative electrode and monocell were manufactured using the same method as in Example 1, except that the width L of the engraved shape 21 was set to approximately 500 μm and the depth D to 30 μm.

[0109] Example 3 The negative electrode and monocell were manufactured using the same method as in Example 1, except that the width L of the engraved shape 21 was set to approximately 500 μm and the depth D to approximately 50 μm.

[0110] Example 4 The negative electrode and monocell were manufactured using the same method as in Example 1, except that the width L of the engraved shape 21 was set to approximately 1,000 μm and the depth D was set to approximately 10 μm.

[0111] Comparative Example 1 The negative electrode and monocell were manufactured using the same method as in Example 1, except that an incised shape was not formed.

[0112] Comparative Example 2 The negative electrode and monocell were manufactured using the same method as in Example 1, except that the width L of the engraved shape 21 was set to approximately 500 μm and the depth D to approximately 90 μm.

[0113] Comparative Example 3 The negative electrode and monocell were manufactured using the same method as in Example 1, except that the width L of the engraved shape 21 was set to approximately 1,000 μm and the depth D was set to approximately 30 μm.

[0114] Comparative Example 4 The negative electrode and monocell were manufactured using the same method as in Example 1, except that the width L of the engraved shape 21 was set to approximately 1,000 μm and the depth D was set to approximately 50 μm.

[0115] Comparative Example 5 The negative electrode and monocell were manufactured using the same method as in Example 1, except that the width L of the engraved shape 21 was set to approximately 1,000 μm and the depth D was set to approximately 90 μm.

[0116] Comparative Example 6 The negative electrode and monocell were manufactured using the same method as in Example 1, except that the width L of the engraved shape 21 was set to approximately 90 μm and the depth D to approximately 55 μm.

[0117] Comparative Example 7 The negative electrode and monocell were manufactured using the same method as in Example 1, except that the width L of the engraved shape 21 was set to approximately 2,500 μm and the depth D was set to approximately 2 μm.

[0118] The width L, depth D, and volume Vp of the incised shape 21, as well as the ratio of the volume Vp of the incised shape to the volume V of the active material layer (Vp / V) of the incised shape and comparative examples were confirmed and summarized in Table 1 below.

[0119] The width L, depth D, and volume ratio (Vp / V) of the engraved shape 21 were measured using a laser microscope.

[0120] As described above, a KEYENCE VR-3000 laser microscope was used, and the measurement was performed with a scan range of 2 cm × 2 cm and a high-magnification camera magnification of × 40, ensuring that the engraved shape 21 was included.

[0121] Figure 6 shows an example of scanning the engraved shape 21 with the measuring device, which can measure the width L, depth D, and volume ratio (Vp / V) of the engraved shape 21.

[0122] [Table 1]

[0123] Test Example 1. Impregnation The impregnation properties of the electrodes in the examples and comparative examples were confirmed by evaluating factors such as impregnation rate, impregnation time, and area of ​​the impregnated region.

[0124] The aforementioned impregnation properties were evaluated using the following method. 1 μl of propylene carbonate (PC) was dropped onto the incised shape 21 of electrode 1 of the example or comparative example at room temperature (25°C), and the time until impregnation was completed (impregnation time) was measured while maintaining the temperature. The completion of impregnation was defined as the point when the area where the propylene carbonate (PC) was dropped was wet enough that the propylene carbonate (PC) did not stick to the hand when touched.

[0125] Furthermore, the dropping was performed on the central point in the width direction of the incised shape 21, and the propylene carbonate (PC) was dropped using a dropper at a height of approximately 4 cm away from the surface on which the propylene carbonate (PC) was dropped, allowing it to fall naturally. In the case of Comparative Example 1, since there was no incised shape, the dropping was performed on the surface of the active material layer.

[0126] As described above, after the impregnation was completed, the impregnated region was formed in an elliptical shape in all cases except for Comparative Example 1. Here, the impregnated region refers to the wetting region in a planar shape observed from the direction of the surface from which the propylene carbonate (PC) was dropped (see Figure 2). The major axis (L) of this elliptical shape is the major line (L). maj ) and minor axis (minor line, L min ) ratio (L maj / L min ) was measured (in the case of Comparative Example 1, the impregnation area was formed in the shape of a circle and the ratio was shown as 1).

[0127] The impregnation rate V was measured using the following equation 2. [Formula 2] V=S p / t p

[0128] In Equation 2, the S p is the area of ​​the impregnation region, and t p This is the time required from the time of application until impregnation is complete.

[0129] The above information is summarized in Table 2 below. The ratio of the major axis to the minor axis in Table 2 was evaluated after measuring the major axis and minor axis (diameter in the case of a circle) using a steel ruler, and the area of ​​the impregnation region was calculated and evaluated using the measured major axis and minor axis (diameter in the case of a circle).

[0130] [Table 2]

[0131] From Tables 1 and 2, Examples 1 to 4, in which the ratio of the volume Vp of the incised shape to the volume V of the active material layer (100 × Vp / V) is in the range of 0.1 to 0.6, showed an impregnation rate V of 1.5π mm in the impregnation evaluation. 2 / s~9.5πmm 2 Points formed within the range of / s can be confirmed. On the other hand, in the case of Comparative Example 1, which did not have an incised shape, a slow impregnation rate was confirmed, and in Comparative Examples 2 to 5, where the ratio (100 × Vp / V) exceeded 0.6, an excessively fast impregnation rate V was confirmed, and a large area of ​​the impregnated region was also confirmed. Furthermore, as can be seen from Tables 1 and 2, although the ratio (100 × Vp / V) is within the range of 0.1 to 0.6, in Comparative Example 6, which is narrower in width and deeper than Example 1, the length of the long axis is significantly longer than the length of the short axis, and a slightly lower impregnation rate V was observed.

[0132] Furthermore, Tables 1 and 2 show that although the ratio (100 × Vp / V) is within the range of 0.1 to 0.6, Comparative Example 7, which has a longer width and shallower depth compared to Example 1, had a slower impregnation rate because the effect of the incised shape could not be obtained.

[0133] Test Example 2. Evaluation of Lithium Deposition The monocells of the examples and comparative examples were charged and discharged to evaluate the presence or absence of lithium deposition, and the results are shown in Table 3.

[0134] The charging and discharging conditions were modified as shown in Table 3 below, and the charge and discharge cycles were performed for 7 cycles under each condition, and the results were checked. In Table 3 below, ○ indicates that precipitation occurred, and × indicates that precipitation did not occur.

[0135] [Table 3]

[0136] Table 3 shows that in the comparative example, lithium deposition always occurred depending on the charging conditions. Therefore, these results indicate that lithium deposition can be stably prevented when an incised shape is formed according to the method of this embodiment.

[0137] Test Example 3. Battery Life Evaluation The monocells of the examples and comparative examples were repeatedly charged and discharged at room temperature (25°C) under conditions of 0.33C / 0.5C per cycle, and the resulting retention capacity is shown in Figure 7. From Figure 7, it can be confirmed that when the electrodes of Examples 1 to 4 are applied, the retention rate of the remaining retention capacity per cycle is superior to that of the comparative examples. On the other hand, comparative examples 6 and 7 showed results similar to comparative example 1 during the life evaluation. [Explanation of Symbols]

[0138] 1: Electrode 20: Active material layer 10: Current collector 21: Intaglio shape

Claims

1. The current collector and the active material layer formed on at least one surface of the current collector are included. The active material layer has an engraved shape, The width of the aforementioned incised shape is in the range of 100 μm to 2,000 μm. The thickness of the active material layer is in the range of 50 μm to 200 μm. The ratio of the depth D of the incised shape to the thickness T of the active material layer (D / T) is within the range of 0.1 to 0.

6. When the width of the engraved shape is within the range of 100 μm to 800 μm, the ratio of the depth D of the engraved shape to the width L (D / L) is within the range of 0.005 to 0.15, and when the width of the engraved shape exceeds 800 μm, the ratio of the depth D of the engraved shape to the width L (D / L) is within the range of 0.005 to 0.

025. An electrode for a non-aqueous electrolyte lithium-ion secondary battery that satisfies the relationship shown in Equation 1 below: [Formula 1] 0.1 ≤ 100 × Vp / V ≤ 0.6 In Equation 1, Vp is the volume of the engraved shape, and V is the volume of the active material layer.

2. The electrode according to claim 1, wherein one or more incised shapes are formed thereon.

3. The active material layer contains electrode active material and binder. The aforementioned binder has a solubility parameter of 10 to 30 MPa. １／２ The electrode according to claim 1, which is within the range.

4. The electrode according to claim 3, wherein the ratio of electrode active material in the active material layer is 80 to 99% by weight, and the binder is included in an amount of 0.1 to 10 parts by weight relative to 100 parts by weight of the electrode active material.

5. The electrode according to claim 3, wherein the electrode active material contains graphite.

6. The current collector and the active material layer formed on at least one surface of the current collector are included. The active material layer has an engraved shape, The thickness of the active material layer is in the range of 50 μm to 200 μm. The ratio of the depth D of the incised shape to the thickness T of the active material layer (D / T) is in the range of 0.1 to 0.6, and the width of the incised shape is in the range of 100 μm to 2,000 μm. If the width of the engraved shape is within the range of 100 μm to 800 μm, the ratio of the depth D of the engraved shape to the width L (D / L) is within the range of 0.005 to 0.15, and if the width of the engraved shape exceeds 800 μm, the ratio of the depth D of the engraved shape to the width L (D / L) is within the range of 0.005 to 0.

025. V, calculated using Equation 2 below, is 1.5π mm. ２ / s ~ 9.5π mm ２ Electrodes for non-aqueous electrolyte lithium-ion secondary batteries, within the range of / s: [Formula 2] V=S ｐ / t ｐ In equation 2, S ｐ This is the area of ​​the propylene carbonate (PC) impregnation region, which was confirmed by dropping 1 μl of propylene carbonate (PC) onto the incised shape of the electrode at 25°C. ｐ This is the time required from the time of dropping until impregnation.

7. The S of Formula 2 ｐ is less than 60π mm ２ The electrode according to claim 6, wherein the S is less than 60π mm

8. t in Equation 2 ｐ The electrode according to claim 6, wherein the time is 25 seconds or less.

9. The impregnation region of propylene carbonate (PC) is elliptical in shape, and the major axis (L) of the elliptical shape is ｍａｊ ) minor axis (L ｍｉｎ ) Ratio (L ｍａｊ / L ｍｉｎ The electrode according to claim 6, wherein the value is greater than 1 and less than or equal to 8.

10. The process includes the step of forming an incised shape on an active material layer formed on at least one surface of the current collector, wherein the thickness of the active material layer is in the range of 50 μm to 200 μm. The ratio of the depth D of the incised shape to the thickness T of the active material layer (D / T) is within the range of 0.1 to 0.

6. A method for manufacturing electrodes for non-aqueous electrolyte lithium-ion secondary batteries, wherein the engraved shape has a width in the range of 100 μm to 2,000 μm, and when the width of the engraved shape is in the range of 100 μm to 800 μm, the ratio of the depth D of the engraved shape to the width L (D / L) is in the range of 0.005 to 0.15, and when the width of the engraved shape exceeds 800 μm, the ratio of the depth D of the engraved shape to the width L (D / L) is in the range of 0.005 to 0.025, and the engraved shape is formed to satisfy the relationship in formula 1 below: [Formula 1] 0.1 ≤ 100 × Vp / V ≤ 0.6 In Equation 1, Vp is the volume of the engraved shape, and V is the volume of the active material layer.

11. A method for manufacturing an electrode according to claim 10, wherein an incised shape is formed by laser irradiation.

12. An electrode assembly comprising a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, An electrode assembly wherein the positive electrode or the negative electrode is an electrode according to any one of claims 1 to 9.

13. A secondary battery comprising the electrode assembly described in claim 12.

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