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

Abstract

The present disclosure relates to a method for manufacturing an electrode for a lithium secondary battery, an electrode for a lithium secondary battery, and a lithium secondary battery including the same, wherein the electrode resistance can be minimized without lowering the electrode density. A method for manufacturing an electrode for a lithium secondary battery according to one embodiment may comprise: a preparation step of forming an electrode active material layer on at least one surface of an electrode current collector; a forming step of forming a plurality of grooves of the electrode active material layer; and a rolling step of rolling the electrode active material layer in which the plurality of grooves are formed in the forming step.

Description

Method for manufacturing electrodes for lithium secondary batteries, electrodes for lithium secondary batteries, and lithium secondary batteries including the electrodes. Technical Field

[0001] This disclosure relates to a method for manufacturing an electrode for a lithium secondary battery, the electrode for a lithium secondary battery, and a lithium secondary battery including the same. More specifically, it relates to a method for manufacturing an electrode for a lithium secondary battery whose lifespan characteristics are not degraded during fast charging, the electrode for a lithium secondary battery, and a lithium secondary battery including the same. Background Technology

[0002] The faster a lithium secondary battery is charged, the shorter the preparation time after discharge for use can be shortened. Therefore, research on fast-charging lithium secondary batteries has received much attention in recent years.

[0003] However, for existing lithium secondary batteries, when charged at a high C-rate, lithium dendrites may form on the surface of the negative electrode due to the negative electrode resistance. This can lead to problems such as the battery capacity decreasing as charge and discharge cycles continue.

[0004] Therefore, there is a need to develop lithium-ion rechargeable batteries whose lifespan characteristics do not decrease during fast charging. Summary of the Invention

[0005] Technical issues

[0006] According to one aspect of this disclosure, an electrode for lithium secondary batteries and a method for manufacturing the same can be provided that minimizes electrode resistance without reducing electrode density.

[0007] According to another aspect of this disclosure, a lithium secondary battery whose lifespan characteristics do not decrease during fast charging can be provided.

[0008] On the other hand, this disclosure can be widely applied to the fields of electric vehicles, battery charging stations, energy storage systems (ESS), and other green technologies that utilize batteries, such as photovoltaic power generation and wind power generation. Furthermore, this disclosure can be used for eco-friendly mobility, including electric vehicles and hybrid vehicles that mitigate climate change by reducing air pollution and greenhouse fluid emissions.

[0009] Technical solution

[0010] The method for manufacturing an electrode for a lithium secondary battery according to the present disclosure may include: a preparation step of forming an electrode active material layer on at least one side of an electrode current collector; a formation step of forming a plurality of grooves in the electrode active material layer; and a calendering step of calendering the electrode active material layer in the formation step that forms the plurality of grooves.

[0011] In a method for manufacturing an electrode for a lithium secondary battery according to one embodiment, the electrode may be a negative electrode.

[0012] In a method for manufacturing an electrode for a lithium secondary battery according to one embodiment, the plurality of grooves can be formed in the forming step such that the pitch between the plurality of grooves is independently greater than 50 μm and less than 200 μm.

[0013] In a method for manufacturing an electrode for a lithium secondary battery according to one embodiment, in the forming step, the depth of the plurality of grooves can be independently greater than 10 μm and less than 250 μm.

[0014] In a method for manufacturing an electrode for a lithium secondary battery according to one embodiment, during the forming step, the width of the plurality of grooves can be independently between 10 μm and 200 μm.

[0015] In a method for manufacturing an electrode for a lithium secondary battery according to one embodiment, the plurality of grooves can be formed in the forming step such that the shape of the plurality of grooves, as observed in cross-section along the thickness direction of the electrode active material layer, independently includes any one of at least a portion of a circle, at least a portion of a quadrilateral, at least a portion of a triangle, and at least a portion of a trapezoid.

[0016] In a method for manufacturing an electrode for a lithium secondary battery according to one embodiment, the plurality of grooves may be formed to have the same shape as each other.

[0017] In a method for manufacturing an electrode for a lithium secondary battery according to one embodiment, the electrode active material layer can be rolled in the rolling step to a first thickness deviation of 4.5% or less, as defined by the following relationship 1.

[0018] [Relation 1]

[0019]

[0020] In the relation 1, T h Ta is the maximum thickness of the electrode after the rolling step, and Ta is the average thickness of the electrode during the preparation step.

[0021] The electrode for a lithium secondary battery according to this disclosure may include: an electrode current collector; and an electrode active material layer formed on at least one side of the electrode current collector, the electrode active material layer including a plurality of grooves and a closed portion corresponding to each of the plurality of grooves.

[0022] In an electrode for a lithium secondary battery according to one embodiment, the electrode may be a negative electrode.

[0023] In an electrode for a lithium secondary battery according to one embodiment, the pitch between the plurality of slots can be independently between 50 μm and 200 μm.

[0024] In an electrode for a lithium secondary battery according to one embodiment, the depth of the plurality of grooves can be independently greater than 10 μm and less than 250 μm.

[0025] In an electrode for a lithium secondary battery according to one embodiment, the width of the plurality of grooves can be independently between 10 μm and 200 μm.

[0026] In an electrode for a lithium secondary battery according to one embodiment, the shape of the plurality of grooves as observed in the cross-section along the thickness direction of the electrode active material layer may independently include any one of at least a portion of a circle, at least a portion of a quadrilateral, at least a portion of a triangle, and at least a portion of a trapezoid.

[0027] In an electrode for a lithium secondary battery according to one embodiment, the shapes of the plurality of grooves may be identical to each other.

[0028] In an electrode for a lithium secondary battery according to one embodiment, the second thickness deviation of the electrode, as defined by the following relationship 2, can be 4.5% or less.

[0029] [Relation 2]

[0030]

[0031] In Equation 2, L4 is the average thickness of the electrode, and L5 is the maximum thickness of the electrode.

[0032] In an electrode for a lithium secondary battery according to one embodiment, the sealing portion can seal the corresponding groove.

[0033] The lithium secondary battery according to this disclosure may include an electrode manufactured according to the manufacturing method of the electrode for lithium secondary batteries according to this disclosure, or an electrode for lithium secondary batteries according to this disclosure.

[0034] Technical effect

[0035] According to one aspect of this disclosure, an electrode for lithium secondary batteries and a method for manufacturing the same can be provided that minimizes electrode resistance without reducing electrode density.

[0036] According to another aspect of this disclosure, a lithium secondary battery whose lifespan characteristics do not decrease during fast charging can be provided.

[0037] On the other hand, this disclosure can be widely applied to the fields of electric vehicles, battery charging stations, energy storage systems (ESS), and other green technologies that utilize batteries, such as photovoltaic power generation and wind power generation. Furthermore, this disclosure can be used for eco-friendly mobility, including electric vehicles and hybrid vehicles that mitigate climate change by reducing air pollution and greenhouse fluid emissions. Attached Figure Description

[0038] Figure 1 is a flowchart illustrating a method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present disclosure;

[0039] Figure 2 is a diagram illustrating a method of forming multiple grooves in the electrode active material layer using a patterned roller in a forming step of a method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present disclosure.

[0040] Figure 3 is a cross-section in the MD direction of an electrode in which multiple grooves are formed in the electrode active material layer according to an embodiment of the formation steps described above;

[0041] Figure 4 is a cross-section in the MD direction of an electrode in which multiple grooves are formed in the electrode active material layer according to another embodiment of the formation steps described above;

[0042] Figure 5 is a cross-section in the MD direction of an electrode in which multiple grooves are formed in the electrode active material layer according to another embodiment of the formation steps described above.

[0043] Figure 6 is a cross-section in the MD direction of an electrode in which multiple grooves are formed in the electrode active material layer according to another embodiment of the formation steps described above.

[0044] Figure 7 is a diagram showing a cross-section in the MD direction of a lithium secondary battery electrode according to an embodiment of the present disclosure in the thickness direction;

[0045] Figure 8 is a diagram showing a cross section in the MD direction of a lithium secondary battery electrode according to another embodiment of the present disclosure in the thickness direction;

[0046] Figure 9 is a diagram showing a cross section in the MD direction of a lithium secondary battery electrode according to another embodiment of the present disclosure in the thickness direction.

[0047] Figure 10 is a diagram showing a cross section in the MD direction of a lithium secondary battery electrode according to another embodiment of the present disclosure in the thickness direction.

[0048] Figure 11 is a SEM image of the surface of an electrode in which multiple grooves are formed in an active material layer according to an embodiment of the present disclosure;

[0049] Figure 12 is a SEM image of the electrode surface after calendering an electrode with multiple grooves formed in the active material layer according to an embodiment of the present disclosure.

[0050] Figure 13 is an XRM image of a cross-section in the thickness direction of an electrode in which multiple grooves are formed in the active material layer according to an embodiment of the present disclosure;

[0051] Figure 14 is an XRM image of a cross section in the electrode thickness direction after calendering an electrode with multiple grooves formed in the active material layer according to an embodiment of the present disclosure.

[0052] Figure 15 is a graph showing the capacity retention of batteries including the negative electrodes of Example 2, Comparative Example 2, and Comparative Example 8.

[0053] Figure 16 is a graph showing the DC-IR values ​​of batteries including the negative electrodes of Example 2, Comparative Example 2, and Comparative Example 8.

[0054] Explanation of reference numerals in the attached figures

[0055] 1: Electrodes for lithium secondary batteries

[0056] 2: First roller

[0057] 3: Second roller

[0058] 100: Electrode current collector

[0059] 200: Electrode active material layer

[0060] 210: slot

[0061] 220: Enclosed section Detailed Implementation

[0062] The embodiments described in this specification can be modified in many other ways, and therefore the technology according to one implementation example is not limited to the embodiments described below. Furthermore, throughout the specification, unless otherwise specifically stated to the contrary, the use of "comprising," "having," "containing," or "having" a component indicates that other components may be included, rather than excluding other components, and does not exclude elements, materials, or works not further listed.

[0063] The numerical ranges used in this specification include lower limits, upper limits and all values ​​within their ranges, increments logically derived within the form and magnitude of the defined range, all values ​​with double limits, and all possible combinations of upper and lower limits of numerical ranges defined in different forms.

[0064] In this specification, unless otherwise defined, “about” may be considered as a value within 30%, 25%, 20%, 15%, 10%, or 5% of the explicitly given value.

[0065] As used in this specification, the term "lithium secondary battery" can refer to a battery that generates electrical energy through the oxidation and reduction reactions of lithium ions during insertion and extraction at the positive and negative electrodes.

[0066] The present disclosure will now be described in detail. However, this is merely an example, and the present disclosure is not limited to the specific embodiments described herein.

[0067] Figure 1 is a flowchart illustrating a method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present disclosure.

[0068] A method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present disclosure may include: a preparation step S100 of forming an electrode active material layer 200 on at least one side of an electrode current collector 100; a formation step S200 of forming a plurality of grooves 210 in the electrode active material layer 200; and a calendering step S300 of calendering the electrode active material layer 200 in which the plurality of grooves 210 are formed in the formation step S200.

[0069] In one embodiment, the preparation step S100 may include a coating step S110 of coating an electrode active material onto at least one side of the electrode current collector 100.

[0070] According to an exemplary embodiment, the electrode current collector 100 may refer to a conductive component that does not cause chemical changes to the secondary battery or secondary cell. The electrode active material may refer to lithium or a compound in which lithium ions can be reversibly intercalated and / or deintercalated. Detailed descriptions of the electrode current collector 100 and the active material will follow.

[0071] According to an exemplary embodiment, in the coating step S110, any known method can be used without particular limitation, as long as it is a method for coating electrode active material onto the current collector in the field of secondary battery technology. Exemplarily, the coating step S110 can be performed using processes such as screen printing, spraying, inkjet printing, thermal transfer printing, offset printing, gravure printing, slot die coating, comma printing, and T-die printing, and is not limited thereto.

[0072] In one embodiment, the preparation step S100 may further include a drying step S120 of drying the electrode current collector 100 on at least one side coated with the electrode active material by the coating step S110. In the drying step S120, as long as the method of drying the electrode current collector coated with the electrode active material is in the field of secondary battery technology, the drying temperature, time, etc. can be performed without particular restrictions.

[0073] In one embodiment, the preparation step S100 may further include a pre-calendering step S130 of calendering the electrode current collector 100 and the active material that have passed through the drying step S120. In the pre-calendering step S130, any known method can be used without particular limitation, as long as it is a method for calendering an electrode current collector coated with electrode active material in the field of secondary battery technology. For example, it can be performed by roll-to-roll calendering, and is not limited thereto.

[0074] In one embodiment, the electrode prepared in preparation step S100 can be formed to an appropriate thickness as needed. Exemplarily, the average thickness of all regions of the electrode prepared in preparation step S100 is defined as T. a When, it can be formed as the T a It has values ​​ranging from 50 μm to 150 μm, specifically from 75 μm to 130 μm, and more specifically from 80 μm to 120 μm.

[0075] In one embodiment, the electrode can be a negative electrode. When the electrode represents a negative electrode, the electrode current collector 100 can represent a negative electrode current collector, and the electrode active material and electrode active material layer 200 can represent a negative electrode active material and a negative electrode active material layer. However, this is not necessarily the case; as needed, the electrode can also represent a positive electrode, or both a negative and a positive electrode. When the electrode represents a positive electrode, the electrode current collector 100 can represent a positive electrode current collector, and the electrode active material and electrode active material layer 200 can represent a positive electrode active material and a positive electrode active material layer. Related details will be described later.

[0076] Figure 2 is a diagram illustrating a method for forming multiple grooves in the electrode active material layer using a patterned roller in a forming step of a method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present disclosure.

[0077] In one embodiment, the forming step S200 may refer to the step of forming a plurality of grooves 210 in the electrode active material layer 200. The forming step S200 is not necessarily limited to this, but as shown in FIG2, pressure can be applied simultaneously between a first roller 2 and a second roller 3 having a plurality of protrusions corresponding to the shape of the grooves 210, through which a lithium secondary battery electrode 1 is passed, to form a plurality of grooves in the electrode active material layer 200.

[0078] Here, multiple protrusions can be formed in at least one of the first roller 2 and the second roller 3.

[0079] As described below, the plurality of grooves 210 can be formed to have specific spacing, depth, and / or width. For this purpose, the plurality of protrusions can be formed in at least one of the first roller 2 and the second roller 3 to form the spacing, depth, and / or width.

[0080] Figure 3 is a cross-section in the MD direction of an electrode in which multiple grooves are formed in the electrode active material layer according to an embodiment of the formation steps.

[0081] In one embodiment, the plurality of grooves 210 may be formed in the forming step S200 such that the spacing L2 between the plurality of grooves 210 is independently greater than 50 μm and less than 200 μm. In a specific embodiment, the plurality of grooves 210 may be formed in the forming step S200 such that the spacing L2 between the plurality of grooves 210 is independently greater than 50 μm and less than 150 μm. In a more specific embodiment, the plurality of grooves 210 may be formed in the forming step S200 such that the spacing L2 between the plurality of grooves 210 is independently greater than 50 μm and less than 100 μm. In one embodiment, the term "spacing" may refer to the distance between the centers of two adjacent grooves 210.

[0082] Referring to Figure 3, the spacing L2 can be defined as the distance between the centers of two adjacent slots 210 in the plurality of slots 210.

[0083] In one embodiment, the plurality of grooves 210 may be formed in the forming step S200, such that the depth L3 of the plurality of grooves 210 is independently greater than 10 μm and less than 250 μm.

[0084] Referring to Figure 3, the depth L3 can be defined as the distance in each groove 210 that is recessed from the surface of the electrode active material layer 200 toward the thickness direction of the electrode active material layer 200.

[0085] In one embodiment, the plurality of grooves 210 may be formed in the forming step S200, such that the width L1 of the plurality of grooves 210 is independently greater than 10 μm and less than 200 μm.

[0086] Referring to Figure 3, the width L1 can be defined as the longest width of the region within each groove 210, based on the surface parallel to the surface of the electrode active material layer 200.

[0087] According to one embodiment of the present disclosure, the electrode for a lithium secondary battery is manufactured such that, when the above-mentioned numerical range is satisfied, it has a structure that facilitates the diffusion of lithium ions into the interior of the negative electrode active material. Therefore, the internal resistance of the electrode is reduced, thereby preventing the formation of lithium dendrites. The capacity retention rate and resistance characteristics of the lithium secondary battery including the electrode for the lithium secondary battery can be significantly improved during fast charging.

[0088] Each groove 210 shown in Figure 3 is illustrated as having a shape including at least a portion of a trapezoid as observed in the cross section, but is not limited thereto, and may be formed to include a variety of shapes as described below.

[0089] Figure 4 is a cross-section in the MD direction of an electrode in which multiple grooves are formed in the electrode active material layer according to another embodiment of the formation steps.

[0090] Figure 5 is a cross-section in the MD direction of an electrode in which multiple grooves are formed in the electrode active material layer according to another embodiment of the formation steps.

[0091] Figure 6 is a cross-section in the MD direction of an electrode in which multiple grooves are formed in the electrode active material layer according to another embodiment of the formation steps.

[0092] In one embodiment, the plurality of grooves 210 may be formed in the forming step S200 such that the shape of the plurality of grooves 210 as observed in the thickness direction section of the electrode active material layer 200 independently includes any one of at least a portion of a circle, at least a portion of a quadrilateral, at least a portion of a triangle, and at least a portion of a trapezoid.

[0093] According to an exemplary embodiment, the thickness direction can refer to a direction perpendicular to the surface or interface from the surface of the electrode active material layer 200 toward the interface between the electrode active material layer 200 and the electrode current collector 100. The thickness direction cross-section can refer to a virtual surface including the thickness direction vector. The thickness direction cross-section can include a MD direction cross-section or a TD direction cross-section of the electrode. The MD direction can refer to a direction parallel to the length direction of the electrode or the delivery direction of the electrode, and the TD direction can refer to the width direction of the electrode or a direction perpendicular to the MD direction with reference to the surface and / or interface. The MD direction cross-section can refer to a virtual surface including the MD direction vector, and the TD direction cross-section can refer to a virtual surface including the TD direction vector.

[0094] Referring to Figure 3, the plurality of grooves 210 can be formed in the forming step S200 such that the shape of the plurality of grooves as observed in the cross section includes at least a portion of a trapezoid.

[0095] Referring to Figure 4, the plurality of grooves 210 can be formed in the forming step S200 such that the shape of the plurality of grooves as observed in the cross section includes at least a portion of a circle.

[0096] Referring to Figure 5, the plurality of grooves 210 can be formed in the forming step S200 such that the shape of the plurality of grooves as observed in the cross section includes at least a portion of a quadrilateral.

[0097] Referring to Figure 6, the plurality of grooves 210 can be formed in the forming step S200 such that the shape of the plurality of grooves as observed in the cross section includes at least a portion of a triangle.

[0098] Unlike Figures 3 to 6, in the forming step S200, the plurality of grooves 210 can be formed such that at least a portion of the plurality of grooves have different shapes when observed in the cross section.

[0099] In one embodiment, the plurality of slots 210 may be formed to have the same shape as each other.

[0100] In one embodiment, the plurality of slots 210 may be configured such that the spacing between the slots 210 is the same.

[0101] In one embodiment, the plurality of grooves 210 may be formed such that all grooves 210 have the same depth.

[0102] In one embodiment, the plurality of slots 210 may be configured such that all slots 210 have the same width.

[0103] According to an exemplary embodiment, the plurality of slots 210 may also be formed in the shape shown in Figures 3 to 6.

[0104] According to an exemplary embodiment, in the formation step S200, during the formation of the plurality of grooves 210, a raised portion, i.e. a protrusion (not shown), may be formed at the boundary between the grooves 210 and the surface of the electrode active material layer 200.

[0105] In one embodiment, the rolling step S300 may refer to the step of rolling the electrode active material layer 200 with a plurality of grooves 210 formed in the forming step S200.

[0106] In the calendering step S300, as described in the pre-calendering step S130, any known method can be used without particular limitation as long as it is a method for calendering an electrode current collector coated with electrode active material in the field of secondary battery technology. For example, it can be carried out by roll-to-roll calendering, and is not limited thereto.

[0107] As described above, during the formation of the plurality of grooves 210 in the forming step S200, protrusions (not shown) can be formed at the boundary between the grooves 210 and the surface of the electrode active material layer 200. In the calendering step S300, by calendering the electrode active material layer 200 that has passed through the forming step S200, mechanical force can be applied to the protrusions (not shown) formed above to form closed portions 220 that correspond adjacently to each of the plurality of grooves 210. That is, a planarized electrode surface can be formed by removing the protrusions (not shown) in the calendering step S300.

[0108] In one embodiment, the electrode active material layer 200 may be rolled in the rolling step S300 such that the first thickness deviation defined by the following relationship 1 is less than 4.5%.

[0109] [Relation 1]

[0110]

[0111] In the relation 1, T h T is the maximum thickness of the electrode after performing the rolling step S300. a It is the average thickness of the electrode in the preparation step S100.

[0112] The T h This can refer to the maximum thickness value observed on the electrode after performing the rolling step S300. As described above, the T... a This can refer to the average thickness value of all regions of the electrode prepared in the preparation step S100. The T... h and / or Ta It can be measured directly with a micrometer, or by measuring the thickness of the cross-section after obtaining a SEM image of the electrode cross-section.

[0113] On the other hand, the first thickness deviation can specifically be less than 4.0%, less than 3.5%, or less than 3.0%. More specifically, the first thickness deviation can be less than 2.0%, less than 1.5%, or less than 1.0%.

[0114] The first thickness deviation can be adjusted by adjusting the rolling pressure, input / output tension, temperature, etc., in the rolling step S300. The pressure, input / output tension, and temperature can be set to conventional conditions used for rolling electrodes in the art.

[0115] When the above-mentioned numerical range is satisfied in the method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present disclosure, the thickness deviation of the manufactured electrode is minimized, and the electrode density can be maintained even when manufacturing a porous electrode. The capacity retention rate and resistance characteristics of the manufactured lithium secondary battery including the electrode for the lithium secondary battery can be significantly improved during fast charging.

[0116] Electrodes for lithium secondary batteries

[0117] Figure 7 is a diagram showing a cross-section in the MD direction of a lithium secondary battery electrode according to an embodiment of the present disclosure in the thickness direction.

[0118] According to one embodiment of the present disclosure, an electrode 1 for a lithium secondary battery includes an electrode current collector 100 and an electrode active material layer 200 formed on at least one side of the electrode current collector 100. The electrode active material layer 200 may include a plurality of grooves 210 and a closed portion 220 adjacent to each of the plurality of grooves 210.

[0119] In one embodiment, the electrode may be the negative electrode.

[0120] According to an exemplary embodiment, the electrode current collector 100 may refer to a negative electrode current collector. Non-limiting examples of negative electrode current collectors include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, and polymer substrates coated with conductive metals. The thickness of the negative electrode current collector may be, for example, 10 to 50 μm, but is not limited thereto.

[0121] According to an exemplary embodiment, the electrode active material layer 200 may include an electrode active material. Herein, the electrode active material layer 200 may refer to a negative electrode active material layer, and the electrode active material may refer to a negative electrode active material. As the negative electrode active material, a material capable of adsorbing and intercalating / deintercalating lithium ions may be used. For example, the negative electrode active material may employ carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers, etc.; lithium metal; lithium alloys; silicon (Si)-containing substances or tin (Sn)-containing substances, etc.

[0122] Examples of the amorphous carbon may include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc.

[0123] Examples of the crystalline carbon may include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0124] The lithium metal may include pure lithium metal or lithium metal formed with a protective layer for suppressing dendrite growth, etc. In one embodiment, a lithium metal-containing layer deposited or coated on the negative electrode current collector may be used as the negative electrode active material layer. In one embodiment, a lithium thin film layer may also be used as the negative electrode active material layer.

[0125] Elements included in the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium, etc.

[0126] The silicon-containing substance may provide further increased capacity characteristics. The silicon-containing substance may include Si, SiOx (0 < x < 2), metal-doped SiO x (0 < x < 2), silicon-carbon composites, etc. The metal may include lithium and / or magnesium, and metal-doped SiO x (0 < x < 2) may include metal silicates.

[0127] Non-limiting examples of the solvent for the negative electrode active material may include water, pure water, deionized water, distilled water, ethanol, isopropyl alcohol, methanol, acetone, n-propanol, tert-butanol, etc.

[0128] The negative electrode active material layer may further include a binder, and may optionally further include a conductive material, a thickener, etc.

[0129] In some embodiments, styrene-butadiene rubber (SBR) based adhesives, carboxymethyl cellulose (CMC), polyacrylic acid based adhesives, and polyethylene dioxythiophene (PEDOT) based adhesives may be used as the adhesives.

[0130] The conductive material can be added to enhance the conductivity of the negative electrode active material layer and / or the mobility of lithium ions or electrons. For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), and carbon fiber, and / or metal-based conductive materials such as perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3, but is not limited thereto.

[0131] Examples of thickeners include carboxymethyl cellulose (CMC).

[0132] In an exemplary embodiment, the electrode may refer to a positive electrode, or a negative electrode and a positive electrode, as needed.

[0133] According to an exemplary embodiment, the electrode current collector 100 may also refer to a positive electrode current collector. The positive electrode current collector may comprise stainless steel, nickel, aluminum, titanium, or alloys thereof. The positive electrode current collector may also comprise aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. The thickness of the positive electrode current collector may be, for example, 10 to 50 μm, but is not limited thereto.

[0134] According to an exemplary embodiment, the electrode active material layer 200 may comprise an electrode active material. Here, the electrode active material layer 200 may also refer to a positive electrode active material layer, and the electrode active material may refer to a positive electrode active material. The positive electrode active material may comprise a compound capable of reversibly inserting and deintercalating lithium ions.

[0135] The positive electrode active material may contain lithium nickel metal oxide. The lithium nickel metal oxide may also contain at least one of cobalt (Co), manganese (Mn) and aluminum (Al).

[0136] In some embodiments, the positive electrode active material or the lithium nickel metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 1.

[0137] [Chemical Formula 1]

[0138] Li x Ni a Mb O 2+z

[0139] In chemical formula 1, the values ​​can be 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b≤0.4, and -0.5≤z≤0.1. As mentioned above, M can include Co, Mn, and / or Al.

[0140] The chemical structure represented by Formula 1 indicates the bonding relationships contained in the layered or crystalline structure of the positive electrode active material, and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn can be provided together with Ni as the main active element of the positive electrode active material. Formula 1 is provided to express the bonding relationships of the main active element and should be understood as including the introduction and substitution of additional elements.

[0141] In one embodiment, an auxiliary element may be further included, added to the main active element to enhance the chemical stability of the positive electrode active material or the layered / crystal structure. The auxiliary element may be incorporated into the layered / crystal structure to form a bond, and it should be understood that this also includes the chemical structures represented by Formula 1.

[0142] The auxiliary element may include, for example, at least one selected from Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. Like Al, the auxiliary element may be used together with Co or Mn as an auxiliary active element to contribute to the capacity / power activity of the positive electrode active material.

[0143] For example, the positive electrode active material or the lithium nickel metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 1-1.

[0144] [Chemical Formula 1-1]

[0145] Li x Ni a M1 b1 M2 b2 O 2+z

[0146] In chemical formula 1-1, M1 may include Co, Mn and / or Al. M2 may include the aforementioned auxiliary elements. In chemical formula 1-1, the values ​​can be 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b1+b2≤0.4, and -0.5≤z≤0.1.

[0147] The positive electrode active material may further include coating elements or doping elements. For example, elements that are substantially the same as or similar to the auxiliary elements may be used as coating elements or doping elements. For example, one or more of the above elements may be used as coating elements or doping elements.

[0148] The coating element or doping element may exist on the surface of the lithium nickel metal oxide particles, or may penetrate through the surface of the lithium nickel metal composite oxide particles to be included in the bonding structure represented by the chemical formula 1 or chemical formula 1-1.

[0149] The positive electrode active material may comprise nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, NCM-based lithium oxide with increased nickel content can be used.

[0150] Ni can be provided as a transition metal related to the power and capacity of lithium secondary batteries. Therefore, by incorporating a high-nickel content (High-Ni) composition into the aforementioned positive electrode active material as described above, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0151] However, with increasing Ni content, the long-term storage stability and lifetime stability of the cathode or secondary battery may decrease relatively, and side reactions with the electrolyte may also increase. According to exemplary embodiments, conductivity can be maintained by including Co while lifetime stability and capacity retention characteristics can be improved by including Mn.

[0152] The Ni content in the NCM-based lithium oxide (e.g., the mole fraction of nickel in the total moles of nickel, cobalt, and manganese) can be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the Ni content can be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0153] In some embodiments, the positive electrode active material may also include lithium cobalt oxide-based active material, lithium manganese oxide-based active material, lithium nickel oxide-based active material, or lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0154] The positive electrode active material layer may further include a positive electrode binder and a conductive material. Depending on the requirements, the positive electrode active material layer may also include a thickener. In some embodiments, the positive electrode binder may include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, butadiene rubber, etc. In one embodiment, PVDF series binders can be used as the positive electrode binder.

[0155] The conductive material can be added to enhance the conductivity of the active material layer and / or the mobility of lithium ions or electrons. For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes (CNTs), vapor-grown carbon fiber (VGCF), and carbon fiber, and / or metal-based conductive materials such as perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3, but is not limited thereto.

[0156] Depending on the requirements, the active material layer may also contain thickeners and / or dispersants. As an example, the active material layer may contain a thickener such as carboxymethyl cellulose (CMC).

[0157] In one embodiment, the electrode active material layer 200 may include a plurality of grooves 210.

[0158] In one embodiment, the spacing L2 between the slots 210 of the plurality of slots 210 can be independently greater than 50 μm and less than 200 μm. In a more specific embodiment, the spacing L2 between the slots 210 of the plurality of slots 210 can be independently greater than 50 μm and less than 150 μm. In a more specific embodiment, the spacing L2 between the slots 210 of the plurality of slots 210 can be independently greater than 50 μm and less than 100 μm.

[0159] Referring to Figure 7, the spacing L2 can be defined as the distance between the centers of two adjacent slots 210 in the plurality of slots 210.

[0160] In one embodiment, the depth L3 of the plurality of grooves 210 can be independently above 10 μm and below 250 μm.

[0161] Referring to Figure 7, the depth L3 can be defined as the distance in each groove 210 that is recessed from the surface of the electrode active material layer 200 in the thickness direction of the electrode active material layer 200.

[0162] In one embodiment, the width L1 of the plurality of slots 210 can be independently greater than 10 μm and less than 200 μm.

[0163] Referring to Figure 7, the width L1 can be defined as the longest width of the region within each groove 210, based on the surface parallel to the surface of the electrode active material layer 200.

[0164] When the electrode for a lithium secondary battery according to one embodiment of the present disclosure satisfies the above-mentioned numerical range, it has a structure that facilitates the diffusion of lithium ions into the interior of the negative electrode active material. Therefore, the internal resistance of the electrode is reduced, thereby preventing the formation of lithium dendrites. The capacity retention rate and resistance characteristics of the lithium secondary battery including the electrode for the lithium secondary battery can be significantly improved during fast charging.

[0165] Figure 8 is a diagram showing a cross section in the MD direction of a lithium secondary battery electrode according to another embodiment of the present disclosure in the thickness direction.

[0166] Figure 9 is a diagram showing a cross-section in the MD direction of a lithium secondary battery electrode according to another embodiment of the present disclosure in the thickness direction.

[0167] Figure 10 is a diagram showing a cross-section in the MD direction of a lithium secondary battery electrode according to another embodiment of the present disclosure in the thickness direction.

[0168] In one embodiment, the shape of the plurality of grooves 210 as observed in a cross-section along the thickness direction of the electrode active material layer 200 may independently include any one of at least a portion of a circle, at least a portion of a quadrilateral, at least a portion of a triangle, and at least a portion of a trapezoid.

[0169] The definitions of the thickness direction and the thickness direction section are the same as those described in the method for manufacturing an electrode for a lithium secondary battery according to an embodiment of this disclosure, and therefore are omitted below.

[0170] Referring to Figure 7, the shape of the plurality of grooves 210 as observed in the cross section may include at least a portion of a trapezoid.

[0171] Referring to Figure 8, the shape of the plurality of grooves 210 as observed in the cross section may include at least a portion of a circle.

[0172] Referring to Figure 9, the shape of the plurality of grooves 210 as observed in the cross section may include at least a portion of a quadrilateral.

[0173] Referring to Figure 10, the shape of the plurality of grooves 210 as observed in the cross section may include at least a portion of a triangle.

[0174] Unlike those shown in Figures 7 to 10, at least some of the plurality of grooves 210 may have different shapes when observed in the cross section.

[0175] In one embodiment, the plurality of slots 210 may have the same shape as each other.

[0176] In one embodiment, the plurality of slots 210 may be configured such that the spacing between the slots 210 is the same.

[0177] In one embodiment, the plurality of grooves 210 may be formed such that all grooves 210 have the same depth.

[0178] In one embodiment, the plurality of slots 210 may be configured such that all slots 210 have the same width.

[0179] According to an exemplary embodiment, the plurality of slots 210 may be formed in the shape shown in Figures 7 to 10.

[0180] In one embodiment, the closure 220 may be formed adjacent to each of the plurality of slots 210.

[0181] As described above, in the forming step S200, during the formation of the plurality of grooves 210, a protrusion (not shown) can be formed at the boundary between the grooves 210 and the surface of the electrode active material layer 200. On the other hand, by rolling the electrode active material layer 200 that has passed through the forming step S200 in the rolling step S300 to apply external force to the protrusion (not shown) formed as above, the closing portion 220 can be formed adjacent to each of the grooves 210.

[0182] In one embodiment, each of the closure portions 220 can seal the corresponding groove 210.

[0183] Therefore, as shown in Figure 11 below, the plurality of grooves 210 are not visible on the electrode surface. With this structure, an electrode for a lithium secondary battery according to an embodiment of the present disclosure can have a planarized surface while forming a plurality of grooves internally.

[0184] In contrast, each of the closed portions 220 may also include a partial opening area that exposes a portion of the interior of the corresponding groove 210.

[0185] In one embodiment, the second thickness deviation of the electrode, as defined by the following Equation 2, may be less than 4.5%.

[0186] [Relation 2]

[0187]

[0188] In Equation 2, L4 is the average thickness of the electrode, and L5 is the maximum thickness of the electrode.

[0189] L4 can refer to the average thickness value across all regions of the electrode. L5 can refer to the maximum thickness value observed on the electrode. L5 can be defined as T in relation 1 above. h The same meaning applies. L4 and / or L5 can be measured directly with a micrometer, or by measuring the cross-sectional thickness after obtaining a SEM image of the electrode cross-section.

[0190] On the other hand, the second thickness deviation can specifically be less than 4.0%, less than 3.5%, or less than 3.0%. More specifically, the second thickness deviation can be less than 2.0%, less than 1.5%, or less than 1.0%.

[0191] The lithium secondary battery electrode according to one embodiment of the present disclosure can be an electrode manufactured according to the manufacturing method of the lithium secondary battery electrode according to one embodiment of the present disclosure. The lithium secondary battery electrode according to one embodiment of the present disclosure has a structure that facilitates lithium-ion diffusion because it includes multiple grooves 210 internally, but by having a smooth surface to minimize thickness deviation, it is possible to achieve improved cell performance while maintaining electrode density.

[0192] Lithium secondary batteries

[0193] A lithium secondary battery according to one embodiment of the present disclosure may include an electrode manufactured according to a manufacturing method according to one embodiment of the present disclosure or an electrode according to one embodiment of the present disclosure.

[0194] A lithium secondary battery according to one embodiment of the present disclosure may include a negative electrode, a positive electrode, and an electrolyte. The negative electrode and / or positive electrode may be an electrode for a lithium secondary battery according to one embodiment of the present disclosure or an electrode manufactured according to a method for manufacturing an electrode for a lithium secondary battery according to one embodiment of the present disclosure.

[0195] In one embodiment, the negative electrode may be an electrode for a lithium secondary battery according to an embodiment of the present disclosure or an electrode manufactured according to a method for manufacturing an electrode for a lithium secondary battery according to an embodiment of the present disclosure.

[0196] Since the negative or positive electrode is the same as described above, the following description is omitted.

[0197] The electrolyte can be housed together with an electrode assembly consisting of the positive electrode, the negative electrode, and the separator described below within a housing to define a lithium secondary battery according to one embodiment of the present disclosure. According to an exemplary embodiment, a non-aqueous electrolyte can be used as the electrolyte.

[0198] The non-aqueous electrolyte comprises a lithium salt as the electrolyte and an organic solvent, wherein the lithium salt is, for example, represented by Li. + X - As the anion of the lithium salt (X) - ), which can be exemplified by F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3) 5PF - (CF3) 6P - CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5) 3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 - SCN - and (CF3CF2SO2)2N - wait.

[0199] The organic solvent may include an organic compound that has sufficient solubility for the lithium salt and additives and is non-reactive in the battery. For example, the organic solvent may include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, and aprotic solvents. As the organic solvent, for example, propylene carbonate (PC), ethylene carbonate (EC), butene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, vinylene carbonate, methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), ethyl fluoroacetate (FEA), ethyl difluoroacetate (DFEA), ethyl trifluoroacetate (TFEA), dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), and diethylene glycol dimethyl ether can be used. These include ether (DEGDME), dimethoxyethane, tetrahydrofuran (THF), 2-methyltetrahydrofuran, ethyl alcohol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, γ-butyrolactone, and propylene sulfite, etc. These can be used alone or in combination of two or more.

[0200] The non-aqueous electrolyte may further contain additives. These additives may include, for example, cyclic carbonate compounds, fluorinated carbonate compounds, sulopentalide compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, and borate ester compounds.

[0201] A lithium secondary battery according to one embodiment of the present disclosure may include a separator. The separator may be configured to prevent electrical short circuits between the positive and negative electrodes and to allow ion flow. According to embodiments, the thickness of the separator may be from 10 μm to 20 μm, but the present disclosure is not limited thereto.

[0202] For example, the diaphragm may comprise a porous polymer membrane or a porous nonwoven fabric. The porous polymer membrane may comprise polyolefin polymers such as ethylene polymers, propylene polymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers. The porous nonwoven fabric may comprise high-melting-point glass fibers, polyethylene terephthalate fibers, etc. The diaphragm may also comprise ceramic materials. For example, inorganic particles may be coated on or dispersed within the polymer membrane to improve heat resistance.

[0203] The diaphragm may have a single-layer or multi-layer structure comprising the polymer membrane and / or nonwoven fabric.

[0204] According to exemplary embodiments, an electrode assembly can be formed by repeatedly configuring a positive electrode, a negative electrode, and a separator. In some embodiments, the electrode assembly can be of the winding type, stacking type, z-folding type, or stack-folding type.

[0205] In one implementation of the present disclosure, the electrode assembly in a lithium secondary battery can be built into a housing and sealed.

[0206] The outer casing can be, for example, a pouch-shaped casing, a prismatic casing, a cylindrical casing, a coin-shaped casing, etc.

[0207] According to one implementation example of this disclosure, the lithium secondary battery can be used not only as a cell for powering small devices, but also preferably as a unit battery in a battery module of a medium to large device comprising multiple cells. Examples of such small devices include mobile phones, laptops, and cameras, while examples of such medium to large devices include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems, but are not limited to these.

[0208] The embodiments of this disclosure are further illustrated below with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are only for illustrating the invention and are not intended to limit the scope of the appended claims. Various changes and modifications can be made to the embodiments within the scope and technical concept of this disclosure, which will be obvious to those skilled in the art, and such variations and modifications are naturally within the scope of the appended claims.

[0209] Manufacturing example

[0210] (1) Preparation of the negative electrode

[0211] A negative electrode active material slurry was prepared by mixing artificial graphite, silicon dioxide (SiO2), single-walled carbon nanotubes (SWCNT), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a weight ratio of 92:4.5:0.5:1.5:1.5 and dispersing them in distilled water.

[0212] The prepared slurry was fed into a slot die at a concentration of 10 mg / m³. 2 After being coated on both sides of a copper thin film, the anode was finally manufactured by calendering after drying at a predetermined temperature. The anode has a thickness of 100 μm.

[0213] (2) Preparation of the positive electrode

[0214] Will Li[Ni 0.88 Co 0.10 Mn 0.02 A positive electrode active material slurry was prepared by mixing O2, carbon black, and polyvinylidene fluoride (PVdF) in a weight ratio of 96:3:1. The prepared slurry was uniformly coated on both sides of an aluminum film, dried at a predetermined temperature, and then calendered to finally produce a positive electrode with a thickness of 100 μm.

[0215] Example

[0216] (Examples 1 to 7)

[0217] Multiple grooves were formed in the negative electrode active material layer of the negative electrode prepared in the manufacturing example using a pattern roller. The negative electrode with multiple grooves formed above was then rolled again using a roll press to finally manufacture the negative electrode.

[0218] (Comparative Examples 1 to 7)

[0219] The negative electrode was ultimately manufactured by forming multiple grooves in the negative electrode active material layer prepared in the manufacturing example using a patterned roller.

[0220] (Comparative Example 8)

[0221] No additional subsequent processes were performed to prepare the negative electrode manufactured in the manufacturing example.

[0222] The spacing of the grooves formed on the negative electrodes finally manufactured in Examples 1 to 7 and Comparative Examples 1 to 7 is shown in Table 1 below. Furthermore, the spacing is determined by the spacing of the protrusions formed on the patterned roller.

[0223] Table 1

[0224]

[0225] Evaluation Example 1: Evaluation of Electrode Thickness Deviation Mitigation

[0226] Figure 11 is a SEM image of the surface of an electrode in which multiple grooves are formed in an active material layer according to an embodiment of the present disclosure.

[0227] Figure 12 is a SEM image of the electrode surface after calendering an electrode with multiple grooves formed in the active material layer according to an embodiment of the present disclosure.

[0228] Figure 13 is an XRM image of a cross-section in the thickness direction of an electrode in which multiple grooves are formed in the active material layer according to an embodiment of the present disclosure.

[0229] Figure 14 is an XRM image of a cross-section in the electrode thickness direction after calendering an electrode with multiple grooves formed in the active material layer according to an embodiment of the present disclosure.

[0230] Specifically, Figure 11 is a scanning electron microscope (SEM, Apreo 2S, Thermo Fisher Scientific) image of the negative electrode of Comparative Example 4, and Figure 12 is the SEM image of the negative electrode of Example 4. Figure 13 is an X-ray microscope (XRM, Xradia 620, ZEISS) image of the negative electrode of Comparative Example 4, and Figure 14 is the XRM image of the negative electrode of Example 4.

[0231] As shown in Figures 11 and 13, for electrodes that have undergone only the forming step of this disclosure in the manufacturing method of electrodes for lithium secondary batteries, multiple grooves are observed on the electrode surface, and the boundary portions of the grooves and the surface are observed to be raised relative to other areas. However, as shown in Figures 12 and 14, for electrodes that have undergone a rolling step after the forming step according to an embodiment of this disclosure, no grooves are observed on the electrode surface, and it can be confirmed that the overall electrode surface is smooth.

[0232] On the other hand, the maximum thickness of the negative electrodes of Examples 1 to 7 and Comparative Examples 1 to 7, and the rate of increase in thickness compared to Comparative Example 8, were measured and calculated, and recorded in Table 2 below. The thicknesses were measured based on SEM images of the cross-sections of each negative electrode.

[0233] Table 2

[0234]

[0235] As shown in Table 2, it can be confirmed that Examples 1 to 7, which are electrodes that undergo a rolling step after the forming step according to an embodiment of the present disclosure, have a smaller electrode thickness increase rate compared to Comparative Examples 1 to 7, which are electrodes that have not undergone a rolling step. In particular, Examples 1 and Comparative Examples 1, Examples 2 and Comparative Examples 2, Examples 3 and Comparative Examples 3, Examples 4 and Comparative Examples 4, Examples 5 and Comparative Examples 5, Examples 6 and Comparative Examples 6, Examples 7 and Comparative Examples 7 correspond to combinations of examples and comparative examples that are directly comparable because they form grooves with the same pattern. It can be confirmed that in each combination, Examples 1 to 7 have a significantly smaller thickness increase rate compared to their corresponding Comparative Examples 1 to 7.

[0236] Evaluation Example 2: Lifetime Characteristics Evaluation

[0237] 1. Capacity retention evaluation

[0238] Figure 15 is a graph showing the capacity retention of batteries including the negative electrodes of Example 2, Comparative Example 2, and Comparative Example 8.

[0239] Lithium-ion secondary batteries, including the negative electrodes of Example 2, Comparative Example 2, and Comparative Example 8, were manufactured respectively. Specifically, each negative electrode and the positive electrode prepared in the manufacturing example were notched and stacked at a predetermined size, and a separator (PE, 25 μm) was inserted between the positive and negative electrode plates to manufacture each battery. The electrolyte used was prepared by adding 1 wt% vinylene carbonate (VC), 0.5 wt% 1,3-propenyl sulpholol (PRS), and 0.5 wt% lithium bis(oxalate)borate (LiBOB) to a 1M LiPF6 solution prepared using a solvent containing ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) in a volume ratio of 25:45:30.

[0240] The discharge capacity was measured by repeating 400 charge (CC / CV 2.0C 4.2V 0.1C cut-off) and discharge (CC 0.33C 2.5V cut-off) cycles on each battery, including each negative electrode. The capacity retention rate was calculated as the percentage of the discharge capacity divided by the value of the first discharge capacity.

[0241] The capacity retention rates of each battery, including the negative electrodes of Example 2, Comparative Example 2, and Comparative Example 8, are recorded in Table 3 below.

[0242] Table 3

[0243]

[0244] As shown in Figure 15 and Table 3, it can be confirmed that the battery of Example 2, which includes a negative electrode exhibiting a thickness increase rate of less than 4.5% after a rolling step following the formation of multiple grooves according to an embodiment of this disclosure, has a significantly improved capacity retention rate compared to the battery of Comparative Example 2, which includes a negative electrode without a rolling step, or even Comparative Example 8, which did not undergo a groove formation step. It is believed that this is because the electrode with multiple grooves formed on the active material layer has a structure that is conducive to lithium-ion diffusion compared to electrodes not constructed in this way, and the electrode with a smooth surface obtained by further rolling after the formation of multiple grooves, despite having grooves, can maintain the electrode density of the case without grooves.

[0245] 2. DC-IR Evaluation

[0246] Figure 16 is a graph showing the DC-IR values ​​of batteries including the negative electrodes of Example 2, Comparative Example 2, and Comparative Example 8.

[0247] Lithium-ion secondary batteries, including the negative electrodes of Example 2, Comparative Example 2, and Comparative Example 8, were manufactured respectively. Specifically, each negative electrode and the positive electrode prepared in the manufacturing example were notched and stacked at a predetermined size, and a separator (PE, 25 μm) was inserted between the positive and negative electrode plates to manufacture each battery. The electrolyte used was prepared by adding 1 wt% vinylene carbonate (VC), 0.5 wt% 1,3-propenyl sulpholol (PRS), and 0.5 wt% lithium bis(oxalate)borate (LiBOB) to a 1M LiPF6 solution prepared using a solvent containing ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) in a volume ratio of 25:45:30.

[0248] The DC-IR value was measured at 25°C after each battery, including each negative electrode, underwent 400 cycles of charging (CC / CV 2.0C 4.2V 0.1C cutoff) and discharging (CC 0.33C 2.5V cutoff).

[0249] The DC-IR values ​​of each battery, including the negative electrodes of Example 2, Comparative Example 2, and Comparative Example 8, are recorded in Table 4 below.

[0250] Table 4

[0251]

[0252] On the other hand, the DC-IR of batteries including the negative electrodes of Examples 1 to 7 and Comparative Example 8 was measured and compared. The configuration of the batteries including each negative electrode was the same as in the evaluation examples described above. Each battery including each negative electrode was charged to 50% SOC at 25°C at 0.33 CCC / CV, and then discharged at a charge-discharge rate of 1C for 10 seconds at 0.33 CCC to measure the DC-IR value of each battery including the negative electrode of Examples 1 to 7. The relative values ​​of the DC-IR values ​​of the batteries including the negative electrodes of Examples 1 to 7 with respect to the DC-IR value of the battery including the negative electrode of Comparative Example 8 are shown in Table 5 below.

[0253] Table 5

[0254]

[0255] As shown in Figure 16 and Table 4, it can be confirmed that the battery of Example 2, which includes a negative electrode exhibiting a thickness increase rate of less than 4.5% after a rolling step following the formation of multiple grooves according to an embodiment of this disclosure, has significantly improved resistance characteristics compared to the battery of Comparative Example 2, which includes a negative electrode without a rolling step, or even Comparative Example 8, which did not undergo a groove formation step. It is believed that this is because the electrode with multiple grooves formed on the active material layer has a structure that is conducive to lithium-ion diffusion compared to electrodes not constructed in this way, and the electrode with a smooth surface obtained by further rolling after the formation of multiple grooves, despite having grooves, can maintain the electrode density of the case without grooves.

[0256] On the other hand, as shown in Table 5, it can be confirmed that a battery comprising a negative electrode with multiple grooves formed such that the spacing between the grooves is greater than 50 μm and less than 200 μm has further improved resistance characteristics compared to an electrode not configured in this way. It is believed that this is because a negative electrode with multiple grooves formed such that the spacing between the grooves meets the data range of this disclosure has a structure more conducive to lithium-ion diffusion than an electrode not configured in this way.

[0257] The above description is merely an example of applying the principles of this disclosure, and other components may be included without departing from the scope of this disclosure.

Claims

1. A method for manufacturing an electrode for a lithium secondary battery, comprising: A preparation step for forming an electrode active material layer on at least one side of the electrode current collector; The step of forming multiple grooves in the electrode active material layer; And the calendering step of forming a multiple groove electrode active material layer in the forming step.

2. The method for manufacturing an electrode for a lithium secondary battery according to claim 1, wherein the electrode is a negative electrode.

3. The method for manufacturing an electrode for a lithium secondary battery according to claim 1, wherein the plurality of grooves are formed in the forming step such that the spacing between the plurality of grooves is independently greater than 50 μm and less than 200 μm.

4. The method for manufacturing an electrode for a lithium secondary battery according to claim 1, wherein the plurality of grooves are formed in the forming step such that the depth of each of the plurality of grooves is independently greater than 10 μm and less than 250 μm.

5. The method for manufacturing an electrode for a lithium secondary battery according to claim 1, wherein the plurality of grooves are formed in the forming step such that the width of each of the plurality of grooves is independently greater than 10 μm and less than 200 μm.

6. The method for manufacturing an electrode for a lithium secondary battery according to claim 1, wherein the plurality of grooves are formed in the forming step such that the shape of the plurality of grooves as observed in cross section in the thickness direction of the electrode active material layer independently includes any one of at least a portion of a circle, at least a portion of a quadrilateral, at least a portion of a triangle, and at least a portion of a trapezoid.

7. The method for manufacturing an electrode for a lithium secondary battery according to claim 6, wherein the plurality of grooves are formed in the same shape as each other.

8. The method for manufacturing an electrode for a lithium secondary battery according to claim 1, wherein in the rolling step, the electrode active material layer is rolled to a first thickness deviation of 4.5% or less as defined by the following formula 1, [Formula 1] In the relation 1, T h Ta is the maximum thickness of the electrode after the rolling step, and Ta is the average thickness of the electrode during the preparation step.

9. An electrode for a lithium secondary battery, comprising: Electrode current collector; An electrode active material layer is formed on at least one side of the electrode current collector, the electrode active material layer including a plurality of grooves and closed portions corresponding to the plurality of grooves respectively.

10. The electrode for a lithium secondary battery according to claim 9, wherein the electrode is a negative electrode.

11. The electrode for a lithium secondary battery according to claim 9, wherein the spacing between the plurality of grooves is independently greater than 50 μm and less than 200 μm.

12. The electrode for a lithium secondary battery according to claim 9, wherein the depth of each of the plurality of grooves is independently greater than 10 μm and less than 250 μm.

13. The electrode for a lithium secondary battery according to claim 9, wherein the width of each of the plurality of grooves is independently greater than 10 μm and less than 200 μm.

14. The electrode for a lithium secondary battery according to claim 9, wherein the shapes of the plurality of grooves as observed in the cross-section along the thickness direction of the electrode active material layer independently include any one selected from at least a portion of a circle, at least a portion of a quadrilateral, at least a portion of a triangle, and at least a portion of a trapezoid.

15. The electrode for a lithium secondary battery according to claim 14, wherein the plurality of grooves have the same shape as each other.

16. The electrode for a lithium secondary battery according to claim 9, wherein the second thickness deviation of the electrode, as defined by the following formula 2, is 4.5% or less, [Formula 2] In Equation 2, L4 is the average thickness of the electrode, and L5 is the maximum thickness of the electrode.

17. The electrode for a lithium secondary battery according to claim 9, wherein the sealing portion seals the corresponding groove.

18. A lithium secondary battery comprising an electrode manufactured according to any one of claims 1 to 8 or an electrode according to any one of claims 9 to 17.

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