An electrode assembly, a lithium secondary battery, a method for manufacturing the electrode assembly and management method of electrode sliding specifications

Abstract

The electrode assembly according to the present invention includes a cathode including a sliding region, and the first cathode thickness ratio RTN1 (=TN1 / TNC), which is the ratio of the thickness TN1 of the cathode composite layer at a first facing position where the cathode faces the bottom part of the anode to the thickness TNC of the cathode composite layer at the center of the cathode, and the first anode thickness ratio RTP1 (=TP1 / TPC), which is the ratio of the thickness TP1 of the anode composite layer at the bottom part of the anode to the thickness TPC of the anode composite layer at the center of the anode, satisfy the following condition 1, thereby effectively preventing the risk of local NP Ratio reversal in the sliding region. [Condition 1] RTN1≥(RTP1 / NP Ratio)×100.1 (In Condition 1 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

Description

Technology Field

[0001] The present invention relates to an electrode assembly for preventing lithium precipitation, a lithium secondary battery including the same, a method for manufacturing the electrode assembly, and a method for managing electrode sliding specifications. Background Technology

[0003] With the increasing technological development and demand in industrial sectors such as mobile devices, automobiles, and energy storage systems, the demand for batteries as energy sources is rapidly rising. Among these secondary batteries, extensive research has been conducted on lithium-ion batteries, which feature high energy density and discharge voltage, and they have been commercialized and are widely used.

[0004] Secondary batteries are classified according to the shape of the battery case into cylindrical and prismatic batteries, in which the electrode assembly is embedded in a cylindrical or prismatic metal can, and pouch-type batteries, in which the electrode assembly is embedded in a pouch-type case made of aluminum laminate sheets.

[0005] In addition, the electrode assembly embedded in the battery case is a power generation element capable of charging and discharging, comprising a stacked structure of a positive electrode, a separator, and a negative electrode. Examples include a jelly-roll type electrode assembly wound with a separator interposed between a long sheet-type positive electrode and a negative electrode coated with an electrode composite containing an electrode active material; a stack type (stacked type) electrode assembly sequentially stacked with a separator interposed between a plurality of positive and negative electrodes punched and notched in units of a predetermined size; and a stack / folding type electrode assembly having a structure in which bi-cells or full cells stacked with a separator interposed between units of positive and negative electrodes in predetermined units are wound.

[0006] The anode and cathode constituting the electrode assembly are manufactured by applying an electrode mixture slurry, prepared in a mixing process, to an electrode current collector in a predetermined pattern and uniform thickness through a slot die, and then drying it. However, since the electrode mixture slurry is a fluid, after the electrode mixture slurry application process, the electrode mixture layer experiences a phenomenon where the electrode mixture slurry flows down due to fluidity, and this is called sliding.

[0007] FIG. 1 shows an electrode sheet with an electrode mixture applied on a sheet-shaped current collector, and FIG. 2 shows a cross-sectional view of the electrode sheet cut along the cutting line (dotted line) of FIG. 1. Referring to these figures, the electrode mixture applied portion (2) has the thickness of the electrode mixture layer gradually decreasing along the direction toward the electrode mixture non-applied portion (1) at both edges in the width direction (x) of the electrode sheet, thereby forming a surface inclined to the plane of the current collector. This is called a sliding area (S), and this sliding area can be formed within 30 mm or within 20 mm along the inner direction of the electrode mixture applied portion from the boundary line between the electrode mixture non-applied portion where the electrode mixture is not applied and the electrode mixture applied portion where the electrode mixture is applied.

[0008] Meanwhile, referring to FIG. 3, the positive electrode (10) and the negative electrode (20) constituting the electrode assembly face each other with a separator (not shown) interposed between them, and the length of the sliding region (S) of the positive electrode and the length of the sliding region (S') of the negative electrode may differ from each other, and the inclined shape of the sliding region may also appear in various forms such as an upward convex shape, a downward convex shape, a straight shape, or an S-shape, and even if the inclined shape is the same, the slope may appear differently. Accordingly, depending on the position of the positive and negative electrodes facing each other, there may be a localized area where the NP Ratio is unbalanced, and the unbalance of the NP Ratio may cause lithium to precipitate from the negative electrode, thereby causing safety accidents such as short circuits.

[0009] Therefore, although it is necessary to develop technology to prevent imbalance in the NP Ratio from the process of manufacturing the anode and cathode, conventionally, there have been limitations in managing the NP Ratio in each unit process of the electrode slurry application process, drying and rolling process, and punching and notching process due to the inconvenience of measuring the thickness of the electrode composite layer in the sliding area and the lack of standardized methods. Therefore, it is necessary to develop technology for an electrode assembly that prevents local imbalance in the NP Ratio in the sliding area during the electrode manufacturing process, and for a method to manage the electrode sliding specifications to prevent imbalance in the NP Ratio. Prior art literature

[0011] International Patent Publication No. 2018-079817 The problem to be solved

[0012] The first problem that the technical concept of the present invention aims to solve is to provide an electrode assembly that prevents the risk of NP Ratio reversal even when the positive and negative electrodes are in the same facing position as before when at least one of the positive and negative electrodes includes a sliding region, a secondary battery including the same, and a method for manufacturing the same.

[0013] The second problem that the technical concept of the present invention aims to solve is to provide a standardized management method for managing sliding specifications to prevent the risk of reversal of the NP Ratio in a manufacturing process of an electrode including a sliding region. means of solving the problem

[0015] According to one embodiment of the present invention, an electrode assembly is provided. The electrode assembly is an electrode assembly for a lithium secondary battery in which a positive electrode and a negative electrode face each other with a separator in between, wherein the protrusion direction of the positive electrode tab and the protrusion direction of the negative electrode tab are opposite to each other. The negative electrode tab includes a negative electrode shoulder portion where a negative electrode composite is coated on a negative electrode current collector and a negative electrode uncoated portion where the negative electrode composite is not coated. The negative electrode shoulder portion includes a negative electrode sliding region that forms an inclined surface on the plane of the negative electrode current collector as the thickness of the negative electrode composite layer decreases along the protrusion direction of the negative electrode tab, and the thickness T of the negative electrode composite layer at the center of the negative electrode NC Regarding the thickness T of the cathode composite layer at the first facing position where the cathode faces the lower part of the anode, the thickness T of the cathode composite layer at the first facing position where the cathode faces the lower part of the anode. N1 The first cathode thickness ratio RT, which is the ratio value of N1 (=T N1 / T NC ) and thickness T of the anode composite layer at the center of the anode PC Regarding the thickness T of the anode composite layer at the lower part of the anode, P1 The first anode thickness ratio RT, which is the ratio value of P1 (=T P1 / T PC ) can satisfy the following condition 1.

[0016] [Condition 1]

[0017] RT N1 ≥(RT P1 / NP Ratio)×100.1

[0018] (In Condition 1 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0019] In an electrode assembly according to one embodiment, the thickness T of the cathode composite layer at the central portion of the cathode NC Regarding the thickness T of the cathode composite layer at the second facing position where the cathode faces the upper part of the anode, the thickness T of the cathode composite layer at the second facing position where the cathode faces the upper part of the anode. N2 The ratio value of the cathode second thickness ratio RT N2 (=TN2 / T NC ) and thickness T of the anode composite layer at the center of the anode PC Regarding the thickness T of the anode composite layer at the upper part of the anode, P2 RT, the ratio value of the anode second thickness ratio P2 (=T P2 / T PC ) can satisfy the following condition 2.

[0020] [Condition 2]

[0021] RT N2 ≥(RT P2 / NP Ratio)×100.1

[0022] (In Condition 2 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0023] In an electrode assembly according to one embodiment, the ratio value of the length L1 of the cathode shoulder line to the length L3 from the first facing position to the end portion of the cathode shoulder line may be 0.5 to 0.9.

[0024] In an electrode assembly according to one embodiment, the anode first thickness ratio RT P1 (=T P1 / T PC ) can be 0.6 to 1.

[0025] In an electrode assembly according to one embodiment, the positive tab of the positive electrode comprises a positive shoulder portion coated with a positive electrode composite on a positive electrode current collector and a positive electrode uncoated portion not coated with a positive electrode composite, and the positive shoulder portion may include a positive electrode sliding region in which the thickness of the positive electrode composite layer is reduced along the protruding direction of the positive electrode tab to form an inclined surface on the plane of the positive electrode current collector.

[0026] According to another embodiment of the present invention, a lithium secondary battery is provided, and the lithium secondary battery may include one or a plurality of electrode assemblies.

[0027] According to another embodiment of the present invention, a method for manufacturing an electrode assembly is provided. The method for manufacturing the electrode assembly comprises: a step of preparing an electrode sheet on an electrode current collector sheet, the electrode sheet comprising an electrode mixture coated portion on which an electrode mixture is coated and an electrode mixture non-coated portion located at least one edge of the electrode mixture coated portion, on which the electrode mixture is not coated; a thickness measurement step of measuring the thickness of each electrode mixture layer at a plurality of points selected at the boundary of the electrode mixture coated portion and the electrode mixture non-coated portion, and measuring the thickness of the electrode mixture layer at the center of the electrode mixture coated portion; an electrode thickness ratio calculation step of calculating ratio values ​​of the thickness of each electrode mixture layer at the plurality of points relative to the thickness of the electrode mixture layer at the center of the electrode mixture coated portion; a step of setting a positive / negative notching line, which sets a notching line to be notched in the form of an individual positive and a individual negative in the positive sheet and the negative sheet based on the calculated positive thickness ratio value and negative thickness ratio value; and a notching step of notching according to the set notching line. A method for manufacturing an electrode assembly comprising a lamination process in which a separator is interposed between a notched anode and a cathode and the electrode is laminated, wherein the process of setting the anode / cathode notching planned lines comprises: determining a first anode face planned line (P3) in an anode sheet and determining a first cathode face planned line (P1) in a cathode sheet; determining the first anode face planned line (P3) as a notching planned line for the anode lower portion; and determining a notching planned line for the cathode upper portion based on the first cathode face planned line (P1), wherein the first cathode face planned line (P1) and the first anode face planned line (P3) are determined such that the cathode thickness ratio in the first cathode face planned line (P1) and the anode thickness ratio in the first anode face planned line (P3) satisfy the following condition 3.

[0028] [Condition 3]

[0029] Cathode thickness ratio ≥ (Anode thickness ratio / NP Ratio) × 100.1

[0030] (In Condition 3 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0031] In a method for manufacturing an electrode assembly according to one embodiment, the process of setting the positive / negative notching planned line may further include the process of tabulating combinations of positive thickness ratio and negative thickness ratio satisfying condition 3 according to a preset NP Ratio value.

[0032] In a method for manufacturing an electrode assembly according to one embodiment, in the process of determining the planned notching line of the upper portion of the cathode, the planned notching line of the upper portion of the cathode may be determined as a virtual line connecting points spaced apart by a planar spacing G1 between the anode and the cathode along the width direction of the cathode sheet from the first planned line facing the cathode.

[0033] In a method for manufacturing an electrode assembly according to one embodiment, the process of setting the positive / negative notching lines may further include the process of determining a second positive face line (P4) in the positive sheet and determining a second negative face line (P2) in the negative sheet, and the second negative face line (P2) and the second positive face line (P4) may be determined such that the ratio of the negative thickness in the second negative face line (P2) and the ratio of the positive thickness in the second positive face line (P4) satisfy condition 3.

[0034] In a method for manufacturing an electrode assembly according to one embodiment, the second cathode facing line (P2) may be determined as a virtual line connecting points spaced apart from the first cathode facing line (P1) by a length C in the electric direction of the anode along the width direction of the cathode sheet.

[0035] In a method for manufacturing an electrode assembly according to one embodiment, the process of setting the positive / negative notching planned line may further include: a process of determining the positive second facing planned line (P4) as the notching planned line of the upper part of the positive electrode; and a process of determining a virtual line connecting points spaced apart by a length A in the electric direction of the negative electrode along the width direction of the negative electrode sheet from the notching planned line of the upper part of the negative electrode as the notching planned line of the lower part of the negative electrode.

[0036] In a method for manufacturing an electrode assembly according to one embodiment, the process of setting the positive / negative notching lines may further include the process of determining the positive tab notching line and the negative tab notching line, and the process of determining the positive tab notching line and the negative tab notching line may be to determine the positive tab notching line such that a positive shoulder line portion coated with a positive compound is included within the positive tab, and to determine the negative tab notching line such that a negative shoulder line portion coated with a negative compound is included within the negative tab.

[0037] In a method for manufacturing an electrode assembly according to one embodiment, the lamination process may include a process of laminating the anodes such that the anode lower portion notching line of the notched anode is positioned on the first face-planning line of the notched cathode.

[0038] In a method for manufacturing an electrode assembly according to one embodiment, the lamination process may include a process of laminating the anodes such that the anode upper portion notching line of the notched anode is positioned on the second face-planning line of the notched cathode.

[0039] According to another embodiment of the present invention, a method for managing electrode sliding specifications is provided. The method for managing electrode sliding specifications is a method for managing the sliding specifications of an electrode including a sliding region in which the thickness of the electrode composite layer gradually decreases to form an inclined surface with respect to the current collector plane, wherein the thickness T of the anode composite layer in the anode central portion of the anode sheetPC and thickness T of the anode composite layer at the planned lower portion of the anode P1 Measure each, and the above T PC T for P1 The first anode thickness ratio RT, which is the ratio value of P1 (=T P1 / T PC A process for calculating ); a process for determining a first cathode facing line (P1) to face the anode lower portion planned portion in the cathode sheet; and a thickness T of the cathode composite layer in the cathode central portion in the cathode sheet. NC and the thickness T of the cathode composite layer at the first cathode face planned line (P1) above. N1 Measure each, and the above T NC The above T regarding N1 The first cathode thickness ratio RT, which is the ratio value of N1 (=T N1 / T NC A process for calculating ); and the first anode thickness ratio RT P1 and the first cathode thickness ratio RT N1 It may include a process of checking whether the relationship satisfies condition 1 below.

[0040] [Condition 1]

[0041] RT N1 ≥(RT P1 / NP Ratio)×100.1

[0042] (In Condition 1 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0043] In a method for managing electrode sliding specifications according to one embodiment, the thickness T of the anode composite layer at the planned upper portion of the anode is given. P2 Measure and the above T PC The above T regarding P2 The second anode thickness ratio RT, which is the ratio value of P2 (=T P2 / T PCA process for calculating ); a process for determining a second cathode facing line (P2) to face the upper part of the anode in the cathode sheet; and a process for determining the thickness T of the cathode composite layer at the second cathode facing line (P2). N2 Measure and the above T NC The above T regarding N2 The second cathode thickness ratio RT, which is the ratio value of N2 (=T N2 / T NC A process for calculating ); and the second anode thickness ratio RT P2 and the second cathode thickness ratio RT N2 The relationship may further include a process of checking whether the relationship satisfies condition 2 below.

[0044] [Condition 2]

[0045] RT N2 ≥(RT P2 / NP Ratio)×100.1

[0046] (In Condition 2 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0047] In a method for managing electrode sliding specifications according to one embodiment, in the process of determining the first cathode face-to-face planned line, the first cathode face-to-face planned line (P1) may be determined as a virtual line connecting points spaced apart along the width direction by the length L1 of the cathode shoulder line portion and the plane-side spacing G1 between the anode and the cathode, from the boundary line between the cathode composite coating portion and the cathode composite non-coating portion.

[0048] In a method for managing electrode sliding specifications according to one embodiment, in the process of determining the second cathode facing line, the second cathode facing line (P2) may be determined as a virtual line connecting points spaced apart from the first cathode facing line (P1) by a length C in the electric direction of the anode along the width direction. Effects of the invention

[0050] The electrode assembly and the method for manufacturing the electrode assembly according to exemplary embodiments of the present invention have the effect of preventing the phenomenon of local reversal of the NP Ratio occurring in the electrode sliding region.

[0051] According to exemplary embodiments of the present invention, the risk of local NP Ratio reversal is ensured by ensuring that the anode thickness ratio and cathode thickness ratio calculated at a specific facing location where the anode and cathode face each other satisfy predetermined conditions, thereby allowing the sliding region where the risk of NP Ratio reversal exists to be managed in a standardized way. Brief explanation of the drawing

[0053] Figure 1 is a top view of an electrode sheet coated with an electrode mixture on a current collector. Figure 2 is a cross-sectional view of an electrode sheet cut along the cutting line (dotted line) of Figure 1. Figure 3 is a conceptual diagram to explain the concept of an imbalance in the NP Ratio occurring in the electrode sliding region. FIG. 4 is a cross-sectional view of an electrode assembly according to one embodiment of the present invention. Figure 5 is a cross-sectional view of the electrode assembly enlarged from part A of Figure 4. Figure 6 is an upper view of part A of Figure 4. Figure 7 is a cross-sectional view of the electrode assembly enlarged from part B of Figure 4. Figure 8 is an upper view of part B of Figure 4. FIGS. 9 and 10 are flowcharts for explaining a method for manufacturing an electrode assembly according to an embodiment of the present invention. FIG. 11 is a drawing for explaining a method for manufacturing an electrode assembly according to one embodiment of the present invention. FIG. 12 is a flowchart for explaining a method for managing electrode sliding specifications according to one embodiment of the present invention. Specific details for implementing the invention

[0054] The present invention will be described in detail below. Prior to this, terms or words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor may appropriately define the concepts of terms to best describe their invention, they must be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0055] In this specification, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only the case where it is "immediately above" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only the case where it is "immediately below" the other part, but also the case where there is another part in between. Additionally, in this application, being placed "on" may include being placed on the lower part as well as on the upper part.

[0056] In this specification, the NP Ratio is a preset value representing the ratio of the cathode capacity to the anode capacity per unit area. This can be determined according to the product specifications, and the NP Ratio has a value of 100% or more, and the % unit is omitted in conditions 1 to 3. The specific numerical range of the NP Ratio may be greater than 100 and less than or equal to 200, greater than 100 and less than or equal to 180, greater than 100 and less than or equal to 160, or 101 to 140.

[0057] In this specification, a sliding region refers to a region at the boundary between an electrode composite non-coated portion where the electrode composite (anode composite layer and cathode composite layer) is not coated and an electrode coated portion where the electrode composite is coated, wherein the thickness of the electrode composite layer is not uniform and gradually decreases as it approaches the electrode composite non-coated portion, thereby forming an inclined surface with respect to the current collector plane.

[0058] In this specification, the anode upper portion refers to the end of the anode edge portion where the anode tab protrudes, and the cathode upper portion also refers to the end of the cathode edge portion where the cathode tab protrudes.

[0059] In this specification, the anode lower portion refers to the end of the anode edge portion facing the anode edge portion where the anode tab protrudes, and the cathode lower portion also refers to the end of the cathode edge portion facing the cathode edge portion where the cathode tab protrudes.

[0060] In this specification, the central portion of the cathode (anode) is a region excluding the sliding region, and is a broad concept referring to an area of ​​the cathode (anode) composite layer where the thickness of the cathode (anode) composite layer does not change and remains constant because the cathode (anode) composite layer is parallel to the plane of the current collector; it does not mean only a specific point in the center of the electric field direction (x) of the cathode (anode).

[0061] In this specification, the width direction of the electrode sheet and the electric field direction of the electrode are defined as the y-axis direction, the transport direction (MD) of the electrode sheet and the electric field direction of the electrode are defined as the x-axis direction, and the thickness direction of the electrode and the thickness direction of the electrode assembly are defined as the z-axis direction.

[0063] (1st embodiment)

[0064] The present invention provides an electrode assembly as a first embodiment.

[0065] FIG. 4 is a cross-sectional view of an electrode assembly according to one embodiment of the present invention, FIG. 5 is a cross-sectional view of the electrode assembly enlarged from part A of FIG. 4, FIG. 6 is a top view of part A of FIG. 4, FIG. 7 is a cross-sectional view of the electrode assembly enlarged from part B of FIG. 4, and FIG. 8 is a top view of part B of FIG. 4.

[0066] Referring to the drawings, an electrode assembly (100) for a lithium secondary battery according to one embodiment of the present invention has a positive electrode (110) and a negative electrode (120) facing each other with a separator (130) in between, wherein the protrusion direction of the positive electrode tab (111) and the protrusion direction of the negative electrode tab (121) are opposite to each other, and the negative electrode tab (121) includes a negative electrode shoulder line portion (121a) on which a negative electrode composite is applied on a negative electrode current collector (121) and a negative electrode uncoated portion (121b) on which a negative electrode composite is not applied, and the negative electrode shoulder line portion (121a) includes a negative electrode sliding region (S') that forms an inclined surface on the plane of the negative electrode current collector as the thickness of the negative electrode composite layer (122) decreases along the protrusion direction of the negative electrode tab (121).

[0067] Generally, electrode assemblies for lithium secondary batteries are managed to have an NP Ratio of 1 or higher to prevent lithium from precipitating during charging and discharging, and especially to prevent rapid degradation of the battery during high-rate charging and discharging. However, when the positive and negative electrodes include a sliding region, a phenomenon of NP Ratio reversal may occur in which the NP Ratio becomes less than 1 locally, depending on the length of the sliding region, the shape of the sliding slope (S-shaped or straight), and the degree of slope. In particular, the risk of NP Ratio reversal may be greater in the sliding region of the negative electrode because the thickness of the negative electrode composite layer is relatively small.

[0068] According to one embodiment of the present invention, when notching a cathode in a cathode sheet, the cathode is manufactured by notching such that a cathode shoulder line portion is included within the cathode tab. This means that the cathode sliding region is cut off when the cathode is notched. Accordingly, the length of the sliding region of the cathode composite layer around the upper portion (12OT) of the cathode according to the present invention is shortened compared to the length of the sliding region of the cathode according to the prior art in which the cathode is notched such that a cathode shoulder line portion does not exist within the cathode tab. Therefore, the electrode assembly according to the present invention can reduce the risk of NP Ratio reversal as the length of the cathode sliding region is shortened. Here, the length of the cathode sliding region refers to the length in which the cathode sliding region extends along the electric field direction (x-axis direction) of the cathode.

[0069] Referring to FIG. 4, the areas in the electrode assembly (100) where NP Ratio reversal is possible are the area (A) where the lower part (110B) of the positive electrode and the upper part (120T) of the negative electrode protruding from the negative electrode tab (121) face each other, and the area (B) where the upper part (110T) of the positive electrode and the lower part (120B) of the negative electrode face each other. Among the facing areas A and B, the likelihood of NP Ratio reversal occurring is higher in the facing area A where the lower part (110B) of the positive electrode and the upper part (120T) of the negative electrode face each other.

[0070] Referring to FIGS. 5 and 7 above, the length of the cathode sliding region (AS') at the facing portion A is longer than the length of the cathode sliding region (BS') at the facing portion B. This is because when the cathode sheet, which serves as the base material for the cathode, is notched into individual cathodes, the cathode shoulder line portion located within the cathode tab retains the sliding region, while the sliding region at the bottom of the cathode is partially cut off. Meanwhile, the length of the anode sliding region (AS) at the facing portion A is shorter than the length of the anode sliding region (BS) at the facing portion B. Accordingly, at the facing portion A, the cathode with a relatively long sliding region and the anode with a relatively short sliding region face each other, so there is a greater possibility that the NP Ratio will be reversed at the facing portion A.

[0071] Accordingly, an electrode assembly according to one embodiment of the present invention is characterized by being designed to satisfy the following condition 1 primarily at the facing portion A. Specifically, the electrode assembly (100) according to one embodiment has a thickness T of the cathode composite layer at the central portion of the cathode. NC Regarding the thickness T of the cathode composite layer at the first facing position where the cathode faces the lower part of the anode, the thickness T of the cathode composite layer at the first facing position where the cathode faces the lower part of the anode. N1 The first cathode thickness ratio RT, which is the ratio value of N1 (=T N1 / T NC ) and thickness T of the anode composite layer at the center of the anode PC Regarding the thickness T of the anode composite layer at the lower part of the anode, P1 The first anode thickness ratio RT, which is the ratio value of P1 (=T P1 / T PC ) can satisfy the following condition 1.

[0072] [Condition 1]

[0073] RT N1 ≥(RT P1 / NP Ratio)×100.1

[0074] (In Condition 1 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0075] The anode and cathode face each other with a separator in between, and in order to prevent NP-Ratio reversal, the capacitance of the cathode must be greater than the capacitance of the anode facing it. However, since it is practically difficult to measure the anode capacitance in the anode's sliding region and the cathode capacitance in the cathode's sliding region separately, it is easier to manage the NP-Ratio by measuring the thickness of the anode composite layer and the cathode composite layer instead of the capacitance in the sliding region. This is because the capacitance of the electrode is proportional to the thickness of the electrode composite layer.

[0076] Even so, it is practically impossible to apply a method for managing the NP Ratio to a mass production process by measuring the thickness of the anode composite layer and the cathode composite layer at every point where the anode and cathode face each other, and checking whether the NP Ratio is satisfied based on the measured values.

[0077] Accordingly, to present an electrode assembly model in which NP Ratio reversal does not occur, the present invention calculates the respective values ​​of the first cathode thickness ratio and the first anode thickness ratio from the thickness of the anode composite layer and the thickness of the cathode composite layer measured at a specific facing position, without the need to measure the thickness of the electrode composite layer at all parts where the anode and cathode face each other, and guarantees that an electrode assembly in which the relationship between them satisfies Condition 1 does not undergo NP Ratio reversal. Furthermore, the first facing position (P1), which is the thickness measurement position for calculating the thickness ratio, is specified as the position facing the lower part (110) of the anode from the cathode (120), and in the case of the anode (110), is specified as the lower part (110B) of the anode.

[0078] That is, the electrode assembly according to the present invention is an electrode assembly designed using the thickness ratio at the "first facing position (P1)" where the positive electrode lower portion (110B) and the negative electrode (120) face each other, and has the effect of preventing the risk of NP Ratio reversal.

[0079] In the present invention, managing the NP Ratio using the thickness ratio rather than the absolute value of the thickness is because the thickness ratio can further ensure the prevention of the risk of NP Ratio reversal. Although the thickness of the anode composite layer or the cathode composite layer measured at a specific facing position cannot gauge the level of sliding, the anode thickness ratio or cathode thickness ratio at a specific facing position can gauge the level of sliding; therefore, the method of managing the NP Ratio using the thickness ratio can further ensure the prevention of the risk of NP Ratio reversal.

[0080] In one specific example, the anode first thickness ratio RT P1 (=T P1 / T PC ) can be 0.6 to 1, and specifically 0.65 to 0.99; 0.7 to 0.98; 0.75 to 0.95; 0.8 to 0.95. In the above-mentioned face portion A, the lower portion (110B) of the anode preferably minimizes the sliding area to increase the energy density of the anode, and accordingly, the first anode thickness ratio, which is the thickness ratio of the lower portion of the anode, has the above numerical range.

[0081] Referring to FIG. 6, in one specific example, the ratio value of the length L1 of the cathode shoulder portion (121a) to the length L3 from the first facing position (P1) to the end portion of the cathode shoulder portion may be 0.5 to 0.9, and specifically, may be 0.65 to 0.8; 0.6 to 0.9; 0.7 to 0.9; or 0.7 to 0.8. In terms of preventing NP Ratio reversal, it is preferable for the length of the cathode shoulder portion to be long.

[0082] An electrode assembly (100) according to one embodiment of the present invention has a thickness T of a cathode composite layer at the center of the cathode. NC Regarding the thickness T of the cathode composite layer at the second facing position where the cathode faces the upper part of the anode, the thickness T of the cathode composite layer at the second facing position where the cathode faces the upper part of the anode. N2 The ratio value of the cathode second thickness ratio RT N2 (=T N2 / T NC ) and thickness T of the anode composite layer at the center of the anode PC Regarding the thickness T of the anode composite layer at the upper part of the anode, P2 RT, the ratio value of the anode second thickness ratio P2 (=T P2 / T PC ) can satisfy the following condition 2.

[0083] [Condition 2]

[0084] RT N2 ≥(RT P2 / NP Ratio)×100.1

[0085] (In Condition 2 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0086] Condition 2 above may be a condition to ensure the prevention of the risk of NP Ratio reversal in the facing area B. As previously mentioned, since the probability of NP Ratio reversal occurring in the facing area B is smaller than that in the opposite area A, Condition 2 may have significance as an auxiliary means of NP Ratio management.

[0087] Referring to FIGS. 7 and 8, the facing portion B is a portion where the positive upper portion (110T) and the negative lower portion (120B) face each other. The positive tab (111) may include a positive shoulder portion (111a) where a positive composite material (112) is applied on the current collector and a positive non-positive portion (111b) where the positive composite material is not applied. The positive shoulder portion (111a) may include a positive sliding area (S) that forms an inclined surface on the plane of the positive current collector as the thickness of the positive composite layer (112) decreases along the protruding direction of the positive tab (111).

[0089] (2nd Example)

[0090] The present invention provides a method for manufacturing an electrode assembly as a second embodiment.

[0091] FIGS. 9 and 10 are flowcharts for explaining a method for manufacturing an electrode assembly according to an embodiment of the present invention, and FIG. 11 is a drawing for explaining a method for manufacturing an electrode assembly according to an embodiment of the present invention.

[0092] Referring to FIG. 9, a method for manufacturing an electrode assembly according to exemplary embodiments of the present invention comprises: a process of preparing an electrode sheet including an electrode composite coating portion and an electrode composite non-coating portion (P110); a thickness measurement process (P120) of measuring the thickness of each electrode composite layer at a plurality of points selected at the boundary between the electrode composite coating portion and the electrode composite non-coating portion, and measuring the thickness of the electrode composite layer at the center of the electrode composite coating portion; an electrode thickness ratio calculation process (P130) of calculating ratio values ​​of the thickness of each electrode composite layer at the plurality of points relative to the thickness of the electrode composite layer at the center of the electrode composite coating portion; a process of setting a positive / negative notching line (P140) of setting a notching line to be notched in the form of an individual positive electrode and an individual negative electrode in the positive sheet and the negative sheet based on the calculated positive / negative notching ratio value and the negative thickness ratio value; and a notching process (P150) of notching according to the set notching line. and a lamination process (P160) in which a separator is interposed between the notched anode and cathode to laminate them.

[0093] According to exemplary embodiments of the present invention, prior to setting the planned notching lines of the positive and negative electrodes, a plurality of points are selected at the boundary between the electrode mixture coated portion and the electrode mixture uncoated portion, and the thickness of the electrode mixture layer is measured at the selected plurality of points to calculate the thickness ratio at each of the plurality of points. Then, by designing the electrode assembly based on the plurality of thickness ratio values ​​calculated in this way, the phenomenon of local NP Ratio reversal occurring in the electrode sliding region can be prevented.

[0094] The process of preparing the electrode sheet (P110) may be a process of preparing an electrode sheet comprising, on an electrode current collector sheet, an electrode mixture coated portion on which an electrode mixture is coated, and an electrode mixture non-coated portion located at least one edge of the electrode mixture coated portion on which the electrode mixture is not coated.

[0095] Specifically, the electrode sheet preparation process (P110) may include a process for preparing a negative electrode sheet and a process for preparing a positive electrode sheet. This electrode sheet preparation process may be prepared by applying an electrode slurry containing an electrode active material onto a sheet-shaped current collector, and then drying and rolling it.

[0096] Referring to FIG. 10, the cathode sheet (20) may include a cathode composite coating portion (22) on which the cathode composite is applied and a cathode composite non-coating portion (21) on which the cathode composite is not applied. The cathode composite non-coating portion (21) may be located at each of the two edges of the cathode composite coating portion with respect to the width direction (x-axis direction) of the cathode sheet. However, it is not limited thereto, and the cathode composite non-coating portion (21) may be located at one edge of the cathode composite coating portion (22). The anode sheet (10) also includes an anode composite coating portion (12) on which the anode composite is applied and a cathode composite non-coating portion (11) on which the anode composite is not applied, similar to the cathode sheet (20). The cathode composite non-coating portion (11) may be located at each of the two edges of the anode composite coating portion (12) or at one edge of the anode composite coating portion (12).

[0097] The thickness measurement process (P120) described above may include a process of selecting a plurality of points at the boundary between the electrode mixture coating portion and the non-coating portion, measuring the thickness of each electrode mixture layer at the selected points, and a process of measuring the thickness of the electrode mixture layer at the center of the electrode mixture coating portion. Here, the boundary between the electrode mixture coating portion and the non-coating portion may be an area where a sliding region exists.

[0098] The thickness measurement process (P120) may include a process of measuring the thickness of the anode composite layer in the anode sheet and a process of measuring the thickness of the cathode composite layer in the cathode sheet.

[0099] Specifically, the process of measuring the thickness of the anode composite layer in the anode sheet may include the process of measuring the thickness of the anode composite layer in the central part of the anode sheet (10) and the process of arbitrarily selecting a plurality of points in the boundary area around the anode composite coating part (12) including a sliding area and the anode composite non-coating part (21) in the anode sheet (10), and measuring the thickness of each anode composite layer at the selected points. At this time, the plurality of points may be selected at regular intervals along the width direction (x-axis direction) of the anode sheet (10).

[0100] Additionally, the process of measuring the thickness of the cathode composite layer in the cathode sheet may include the process of measuring the thickness of the cathode composite layer in the central part of the cathode sheet (20) and the process of arbitrarily selecting a plurality of points in the boundary area around the cathode composite coating part (22) including a sliding area and the cathode composite non-coating part (21) in the cathode sheet (20), and measuring the thickness of each cathode composite layer at the selected points. At this time, the plurality of points may be selected at regular intervals along the width direction (x-axis direction) of the cathode sheet (20).

[0101] After the thickness measurement process (P120) above, the thickness ratio calculation process (P130) above is performed. The thickness ratio calculation process above may include an anode thickness ratio calculation process and a cathode thickness ratio calculation process.

[0102] The above anode thickness ratio is the thickness T of the anode mixture layer at the central part of the anode mixture coating portion. PC Regarding this, it can be defined as the ratio value of the thickness of each anode composite layer at the plurality of points, and the cathode thickness ratio is the thickness T of the cathode composite layer at the central part of the cathode composite coating portion. NC For this, it can be defined as the ratio value of the thickness of each cathode composite layer at the plurality of points. Accordingly, according to the thickness ratio calculation process (P130), the anode thickness ratio of each of the plurality of points and the cathode thickness ratio of each of the plurality of points can be calculated.

[0103] The process of setting the planned notching lines for the positive and negative electrodes (P140) may be a process of setting the planned notching lines for the positive electrodes to be notched in the form of individual positive electrodes (110) in the positive electrode sheet (10) and setting the planned notching lines for the negative electrodes to be notched in the form of individual negative electrodes (120) in the negative electrode sheet (20), based on the positive electrode thickness ratio and negative electrode thickness ratio calculated in the electrode thickness ratio calculation process (P130).

[0104] In the step of setting the planned notching lines of the positive and negative electrodes, since the positive electrode, negative electrode, and separator are not yet laminated, it is not determined which part of the positive electrode sheet and which part of the negative electrode sheet will face each other, and in this state, it is not possible to know whether the relationship between the negative electrode thickness ratio and the positive electrode thickness ratio satisfies condition 3. Therefore, the process of setting the planned notching lines of the positive and negative electrodes (P140) may include the process of determining the part of the positive electrode sheet that will face the negative electrode and the part of the negative electrode sheet that will face the positive electrode.

[0105] Referring to FIGS. 4, 5, and 11, the upper part of the anode sheet (10) can be notched to the anode lower part (110B) with respect to the x-axis direction, and the lower part of the anode sheet (10) can be notched to the anode tab (111) and the anode upper part (110T). The anode lower part (110B) and the anode upper part (110T) can be specific facing positions of the anode according to the present invention. That is, the anode lower part planned line can be the anode first facing line (P3), and the anode upper part planned line can be the anode second facing line (P4).

[0106] Here, the upper positive part refers to the end of the positive edge portion where the positive tab protrudes, and the lower positive part refers to the end of the positive edge portion opposite to the positive edge portion where the positive tab protrudes.

[0107] According to the present invention, an electrode assembly can be designed such that the anode thickness ratio at the first anode face-to-the-post line (P3) and the second anode face-to-the-post line (P4) satisfies condition 3. That is, among the plurality of anode thickness ratio values ​​calculated in the thickness ratio calculation process (P130), a point having an anode thickness ratio that satisfies condition 3 can be located on the first anode face-to-the-post line (P3) and the second anode face-to-the-post line (P4).

[0108] Referring to FIGS. 6, 7, and 11, the cathode (120) is generally cut larger than the anode (110), so when the anode (110) is placed on top of the cathode (120), a portion of the cathode (110) is visible around the outer periphery of the anode (110). With respect to the x-axis direction, the upper part of the cathode sheet (20) can be notched to the cathode tab (121) and the upper part of the cathode (120T), and the lower part of the cathode sheet (20) can be notched to the lower part of the cathode (120B). Also, a first cathode face-to-face line (P1) can be set at the upper part of the cathode sheet (20), and a second cathode face-to-face line (P2) can be set at the lower part of the cathode sheet (20).

[0109] Here, the upper part of the cathode refers to the end of the cathode edge where the cathode tab protrudes, and the lower part of the cathode refers to the end of the cathode edge opposite to the cathode edge where the cathode tab protrudes.

[0110] According to the present invention, an electrode assembly can be designed such that the cathode thickness ratio at the first cathode face-plan line (P1) and the second cathode face-plan line (P2) satisfies condition 3. That is, among the plurality of cathode thickness ratio values ​​calculated in the thickness ratio calculation process (P130), a point having a cathode thickness ratio that satisfies condition 3 can be located on the first cathode face-plan line (P1) and the second cathode face-plan line (P2).

[0111] In the electrode assembly (100) assembled through the above lamination process (P160), the first negative electrode face line (P1) and the first positive electrode face line (P3) may overlap with respect to the horizontal direction (xy) of the electrode assembly. Additionally, the second negative electrode face line (P2) and the second positive electrode face line (P4) may overlap with respect to the horizontal direction (xy) of the electrode assembly.

[0112] Referring to FIG. 10 and FIG. 11, the process of setting the positive / negative notching planned line according to one embodiment (P140) may include: determining a positive first facing planned line (P3) in the positive sheet (10) and determining a negative first facing planned line (P1) in the negative sheet (20) (P141); determining the positive first facing planned line (P3) as a positive lower part notching planned line (P142); and determining a negative upper part notching planned line based on the negative first facing planned line (P1) (P143), wherein the negative first facing planned line (P1) and the positive first facing planned line (P3) may be determined such that the negative thickness ratio in the negative first facing planned line (P1) and the positive thickness ratio in the positive first facing planned line (P3) satisfy the following condition 3.

[0113] [Condition 3]

[0114] Cathode thickness ratio ≥ (Anode thickness ratio / NP Ratio) × 100.1

[0115] (In Condition 3 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0116] That is, among the plurality of cathode thickness ratio values, a point having a cathode thickness ratio satisfying condition 3 can be determined as the first cathode face line (P1), and among the plurality of anode thickness ratio values, a point having an anode thickness ratio satisfying condition 3 can be determined as the first anode face line (P3).

[0117] Condition 3 above is a criterion for ensuring the prevention of NP Ratio reversal of the positive / negative electrodes in the sliding region. A method for manufacturing an electrode assembly according to one embodiment of the present invention can ensure the prevention of NP Ratio reversal by setting a planned line for positive / negative notching based on a specific facing position satisfying Condition 3 and laminating the positive / negative electrodes. In addition, the electrode assembly manufactured accordingly can ensure the prevention of NP Ratio reversal at the area (A) where the lower part (110B) of the positive electrode and the upper part (120T) of the negative electrode with the protruding negative tab (121) face each other.

[0118] According to one embodiment of the present invention, the process of setting the positive / negative notching planned lines (P140) may further include a process of tabulating combinations of positive thickness ratios and negative thickness ratios that satisfy condition 3 according to a preset NP Ratio value. In this case, there is an effect of easily determining the positive first and second facing planned lines and negative first and second facing planned lines that satisfy condition 3.

[0119] For example, if the NP Ratio is set to 108, combinations of anode thickness ratios and cathode thickness ratios satisfying condition 3 can be generated as shown in Table 1. Then, according to the combination in Table 1, the anode first and second facing lines (P3, P4) and cathode first and second facing lines (P1, P2) that serve as references for the notching lines can be determined.

[0120] anode thickness ratio cathode thickness ratio 1 or less 0.93 or higher 0.95 or less 0.88 or higher 0.90 or less 0.83 or higher 0.85 or less 0.79 or higher 0.80 or less 0.74 or higher 0.75 or less 0.70 or higher 0.70 or less 0.65 or higher 0.65 or less 0.60 or higher 0.60 or less 0.56 or higher

[0121] Referring to FIG. 11, the planned notching line of the cathode (dotted line of 120) in the cathode sheet (20) can be set larger than the size of the anode (dotted line of 110) to be notched. The planned notching line of the cathode tab can be located on one side of the cathode composite coating portion (22). Furthermore, the planned notching line of the cathode can be determined according to the length (L1) of the cathode shoulder portion, the length (A) in the cathode's full length direction (x-axis direction), and the length (W1) in the cathode's full width direction (y-axis direction).

[0122] In one embodiment, the length in the electric direction (A) and the length in the width direction (W1) of the cathode may be predetermined lengths, and in determining the length L1 of the cathode shoulder line portion (121a) included within the cathode tab (121) area, the length L1 of the cathode shoulder line portion may be naturally determined based on the cathode first face-to-face planned line (P1) satisfying condition 3. Here, the length of the cathode shoulder line portion may be defined as the length in the extension direction of the cathode shoulder line portion (121a) to which the cathode composite is applied in the cathode tab planned area.

[0123] Referring to FIG. 11, in the process (P143) of determining the planned notching line of the upper portion of the cathode, the planned notching line of the upper portion of the cathode can be determined as a virtual line connecting points spaced apart by a plane gap G1 between the anode and the cathode along the width direction (x-axis direction) of the cathode sheet from the first planned line facing the cathode (P1).

[0124] Referring to FIGS. 10 and 11, the planned notching line (110) of the anode in the anode sheet (10) can be set to be smaller than the size of the cathode (120) to be notched. Additionally, the planned notching line of the anode can be set so that an anode tab (111) is formed on one side of the anode composite coating portion (12). Furthermore, the planned notching line of the anode can be determined according to the length (L2) of the anode shoulder line portion, the length (C) in the anode's full length direction (x-axis direction), and the length (W2) in the anode's full width direction (y-axis direction).

[0125] In one embodiment, the length (C) in the full-length direction of the anode and the length (W2) in the full-width direction of the anode may be predetermined lengths, and in determining the length L2 of the anode shoulder line portion (111b) included within the anode tab area, the length L2 of the anode shoulder line portion may be naturally determined based on the anode second face-planned line (P4) satisfying condition 3.

[0126] According to one embodiment, the process of setting the positive / negative notching planned line (P140) may further include the process (P144) of determining the positive second face-to-positive line (P4) in the positive sheet and determining the negative second face-to-positive line (P2) in the negative sheet. At this time, the negative second face-to-positive line (P2) and the positive second face-to-positive line (P4) may be determined such that the negative thickness ratio in the negative second face-to-positive line (P2) and the positive thickness ratio in the positive second face-to-positive line (P4) satisfy condition 3.

[0127] Accordingly, the electrode assembly manufactured can ensure that the NP Ratio reversal is prevented at the area (B) where the upper part (110T) of the positive electrode and the lower part (120B) of the negative electrode face each other. However, as previously explained, since the possibility of NP Ratio reversal occurring is higher at the aforementioned facing area B than at the facing area B, the process (P144) of determining the second facing planned line (P2) may serve to assist the process of determining the first facing planned line (P1).

[0128] Referring to FIG. 11, the second cathode facing line (P2) can be determined as a virtual line connecting points spaced apart from the first cathode facing line (P1) by a length C in the electric direction of the anode along the width direction of the cathode sheet.

[0129] In one embodiment, the process of setting the positive / negative notching line (P140) may further include a process of determining the notching line of the upper positive portion (P145); and a process of determining the notching line of the lower negative portion (P146).

[0130] Referring to FIG. 11, the planned notching line of the upper part of the anode can be determined as the second planned line facing the anode (P4), and the planned notching line of the lower part of the cathode can be determined as a virtual line connecting points spaced apart from the planned notching line of the upper part of the cathode by a length A in the overall direction of the cathode along the width direction of the cathode sheet.

[0131] In one embodiment, the process of setting the anode / cathode notching planned line may further include a process (P147) of determining the anode tab notching planned line and the cathode tab notching planned line. Referring to FIG. 11, the process of determining the anode tab notching planned line and the cathode tab notching planned line may be to set the anode tab notching planned line so that the anode shoulder line portion (111a) coated with an anode composite material is included within the anode tab (111), and to set the cathode tab notching planned line so that the cathode shoulder line portion (121a) coated with a cathode composite material is included within the cathode tab (121).

[0132] Specifically, the shoulder line portion (121a) of the cathode tab (121) may be included in the inner region of the cathode tab (121) in a form that extends toward the cathode tab uncoated portion (121b) from a virtual line connecting points spaced apart by a predetermined planar spacing G1 between the anode and cathode from the first cathode face-planar line P1. Furthermore, the boundary line between the cathode shoulder line portion (121a) and the cathode uncoated portion (121b) may coincide with the boundary line between the cathode composite coating portion (22) and the cathode composite non-coating portion (21) of the cathode sheet (20) that serves as the base material of the cathode (120).

[0133] Additionally, the shoulder line portion (111a) of the anode tab (111) may be included in the inner region of the anode tab (111) in a form that extends from the anode second face-planned line (P4) toward the anode tab uncoated portion (111b). Furthermore, the boundary line between the anode shoulder line portion (111a) and the anode uncoated portion (111b) may coincide with the boundary line between the anode composite coating portion (12) and the anode composite non-coating portion (11) of the anode sheet (10) that serves as the base material of the anode (110).

[0134] The above notching process (P150) may include an anode notching process in which an individual anode (110) is obtained by notching along a planned anode notching line set according to the above process on an anode sheet (10), and a cathode notching process in which an individual cathode (110) is obtained by notching along a planned cathode notching line set according to the above process on a cathode sheet (20).

[0135] The above lamination process (P160) may be a process of laminating by interposing a separator between the notched anode and cathode.

[0136] The above lamination process (P160) may include a process of laminating the anodes such that the anode lower portion notching line of the notched anode (120) is positioned on the first face-planning line (P1) of the notched cathode (120).

[0137] Additionally, the lamination process (P160) may include a process of laminating the anodes such that the anode upper notching line of the notched anode (120) is positioned on the second face-planning line (P2) of the notched cathode (120).

[0138] The method for manufacturing an electrode assembly according to exemplary embodiments of the present invention can manage electrode sliding specifications in a standardized manner by utilizing specific face-to-face positions of positive and negative electrodes and electrode thickness ratios in an electrode sheet including a sliding region. In addition, the management of NP Ratio inversion in the electrode sliding region can be performed more simply, thereby improving production efficiency.

[0140] (3rd Example)

[0141] The present invention provides a lithium secondary battery as a third embodiment.

[0142] A lithium secondary battery according to exemplary embodiments of the present invention may include one electrode assembly or a laminate in which a plurality of electrode assemblies are stacked.

[0143] According to one embodiment, the electrode assembly is an electrode assembly for a lithium secondary battery in which a positive electrode and a negative electrode face each other with a separator in between, and the protrusion direction of the positive electrode tab and the protrusion direction of the negative electrode tab are opposite to each other, wherein the negative electrode tab includes a negative electrode shoulder portion coated with a negative electrode composite on a negative electrode current collector and a negative electrode uncoated portion not coated with a negative electrode composite, and the negative electrode shoulder portion includes a negative electrode sliding region that forms an inclined surface on the plane of the negative electrode current collector as the thickness of the negative electrode composite layer decreases along the protrusion direction of the negative electrode tab, and the thickness T of the negative electrode composite layer at the center of the negative electrode NC Regarding the thickness T of the cathode composite layer at the first facing position where the cathode faces the lower part of the anode, the thickness T of the cathode composite layer at the first facing position where the cathode faces the lower part of the anode. N1 The first cathode thickness ratio RT, which is the ratio value of N1 (=T N1 / T NC ) and thickness T of the anode composite layer at the center of the anode PC Regarding the thickness T of the anode composite layer at the lower part of the anode, P1 The first anode thickness ratio RT, which is the ratio value of P1 (=T P1 / T PC ) can satisfy the following condition 1.

[0144] [Condition 1]

[0145] RT N1 ≥(RT P1 / NP Ratio)×100.1

[0146] (In Condition 1 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0148] (Fourth Example)

[0149] The present invention provides a method for managing electrode sliding specifications as a fourth embodiment.

[0150] FIG. 12 is a flowchart for explaining a method for managing electrode sliding specifications according to one embodiment of the present invention.

[0151] Referring to FIG. 12, a method for managing electrode sliding specifications according to an exemplary embodiment of the present invention is a method for managing the sliding specifications of an electrode including a sliding region in which the thickness of the electrode composite layer gradually decreases to form an inclined surface with respect to the current collector plane, wherein the thickness T of the anode composite layer in the anode central portion of the anode sheet PC and thickness T of the anode composite layer at the planned lower portion of the anode P1 Measure each, and the above T PC T for P1 The first anode thickness ratio RT, which is the ratio value of P1 (=T P1 / T PC A process for calculating ) (P210); a process for determining a first cathode facing line (P1) to face the anode lower portion planned portion in the cathode sheet (P220); and the thickness T of the cathode composite layer in the cathode central portion in the cathode sheet. NC and the thickness T of the cathode composite layer at the first cathode face planned line (P1) above. N1 Measure each, and the above T NC The above T regarding N1 The first cathode thickness ratio RT, which is the ratio value of N1 (=T N1 / T NC A process for calculating ) (P230); and the first anode thickness ratio RT P1 and the first cathode thickness ratio RT N1It may include a process (P240) to check whether the relationship satisfies the following condition 1.

[0152] [Condition 1]

[0153] RT N1 ≥(RT P1 / NP Ratio)×100.1

[0154] (In Condition 1 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0155] A method for managing electrode sliding specifications according to one embodiment comprises the thickness T of the anode composite layer at the planned upper portion of the anode. P2 Measure and the above T PC The above T regarding P2 The second anode thickness ratio RT, which is the ratio value of P2 (=T P2 / T PC A process for calculating ); a process for determining a second cathode facing line (P2) to face the upper part of the anode in the cathode sheet; and a process for determining the thickness T of the cathode composite layer at the second cathode facing line (P2). N2 Measure and the above T NC The above T regarding N2 The second cathode thickness ratio RT, which is the ratio value of N2 (=T N2 / T NC A process for calculating ); and the second anode thickness ratio RT P2 and the second cathode thickness ratio RT N2 The relationship may further include a process of checking whether the relationship satisfies condition 2 below.

[0156] [Condition 2]

[0157] RT N2 ≥(RT P2 / NP Ratio)×100.1

[0158] (In Condition 2 above, the NP Ratio is a preset value, representing the ratio of cathode capacity to anode capacity per unit area.)

[0159] Referring to FIG. 11, in the process of determining the first cathode face-to-face line according to one embodiment, the first cathode face-to-face line (P1) can be determined as a virtual line connecting points spaced apart from the boundary line of the cathode composite coating part and the cathode composite non-coating part along the width direction by the length L1 of the cathode shoulder line part and the plane-side spacing G1 between the anode and the cathode.

[0160] In addition, in the process of determining the second cathode facing line according to one embodiment, the second cathode facing line (P2) may be determined as a virtual line connecting points spaced apart from the first cathode facing line (P1) by a length C in the electric direction of the anode along the width direction.

[0161] A method for managing electrode sliding specifications according to exemplary embodiments of the present invention can manage electrode sliding specifications in a standardized manner by utilizing specific face-to-face positions of positive and negative electrodes and electrode thickness ratios in an electrode sheet including a sliding area.

[0163] Hereinafter, the present invention will be described with reference to embodiments according to the present invention, but this is for the sake of easier understanding of the present invention and the scope of the present invention is not limited thereto.

[0165] Example 1

[0166] A cathode slurry containing synthetic graphite, SBR binder, CMC thickener, and carbon black is applied onto copper foil, and a cathode sheet is prepared by drying and rolling. LiNi 0.8 Co 0.1 Mn 0.1 An anode slurry containing O2, PVDF binder, and carbon black is applied onto an aluminum foil, and an anode sheet is prepared by drying and rolling.

[0167] The positive electrode electric field length, positive electrode electric field length, negative electrode electric field length, negative electrode electric field length, and the planar gap G1 between the top of the negative electrode and the bottom of the positive electrode are set so that the NP-Ratio of the electrode assembly to be assembled is 108.

[0168] In the prepared cathode sheet, multiple measurement locations were arbitrarily selected at the boundary between the cathode composite coated area and the cathode composite uncoated area, and the thickness of each cathode composite layer was measured at the selected multiple points. Additionally, the thickness of the cathode composite layer at the center of the cathode composite coated area was also measured. Subsequently, cathode thickness ratio values ​​were calculated, which are the ratios of the thickness of the cathode composite layer measured at each of the multiple points to the thickness of the cathode composite layer at the center of the cathode.

[0169] For the prepared anode sheet as well, the thickness of the anode composite layer was measured and the anode thickness ratio values ​​were calculated, just like with the cathode sheet mentioned above.

[0170] A first cathode facing line P1 with a cathode thickness ratio of 0.94 was determined in the cathode sheet, and a first anode facing line P3 with an anode thickness ratio of 0.99 was determined in the anode sheet. Then, a second cathode facing line P2 with a cathode thickness ratio of 0.96 was determined in the cathode sheet, and a second anode facing line P4 with an anode thickness ratio of 0.94 was determined in the anode sheet.

[0171] A virtual line connecting points spaced apart from the above-mentioned first cathode facing line P1 by a predetermined planar spacing G1 between the anode and cathode was determined as the planned notching line for the upper part of the cathode. Then, a virtual line connecting points spaced apart from the above-mentioned planned notching line for the upper part of the cathode by a predetermined length A in the electric direction of the cathode was determined as the planned notching line for the lower part of the cathode. Additionally, the above-mentioned first anode facing line P3 was determined as the planned notching line for the lower part of the anode, and the above-mentioned second anode facing line P4 was determined as the planned notching line for the upper part of the anode.

[0172] The anode and cathode were notched along the notching lines set in this manner, and the anodes were laminated such that the anode lower part notching line of the notched anode was positioned on the cathode first face-to-face line (P1) of the notched cathode, and the anode upper part notching line of the notched anode (110) was positioned on the cathode second face-to-face line (P2) of the notched cathode, thereby completing the manufacture of an electrode assembly.

[0174] Example 2

[0175] In the above Example 1, when determining the first and second cathode facing lines and the first and second anode facing lines, a first cathode facing line P1 with a cathode thickness ratio of 0.89 was determined in the cathode sheet, and a first anode facing line P3 with an anode thickness ratio of 0.94 was determined in the anode sheet. Then, a second cathode facing line P2 with a cathode thickness ratio of 0.93 was determined in the cathode sheet, and a second anode facing line P4 with an anode thickness ratio of 0.90 was determined in the anode sheet. Except for this, an electrode assembly was manufactured in the same manner as in the above Example 1.

[0177] Comparative Example 1

[0178] In the above Example 1, when determining the first and second cathode facing lines and the first and second anode facing lines, a first cathode facing line P1 with a cathode thickness ratio of 0.90 was determined in the cathode sheet, and a first anode facing line P3 with an anode thickness ratio of 0.99 was determined in the anode sheet. Then, a second cathode facing line P2 with a cathode thickness ratio of 0.85 was determined in the cathode sheet, and a second anode facing line P4 with an anode thickness ratio of 0.94 was determined in the anode sheet. Except for this, an electrode assembly was manufactured in the same manner as in the above Example 1.

[0180] Comparative Example 2

[0181] In the above Example 1, when determining the first and second cathode facing lines and the first and second anode facing lines, a first cathode facing line P1 with a cathode thickness ratio of 0.80 was determined in the cathode sheet, and a first anode facing line P3 with an anode thickness ratio of 0.94 was determined in the anode sheet. Then, a second cathode facing line P2 with a cathode thickness ratio of 0.82 was determined in the cathode sheet, and a second anode facing line P4 with an anode thickness ratio of 0.90 was determined in the anode sheet. Except for this, an electrode assembly was manufactured in the same manner as in the above Example 1.

[0183] Experimental Example: Observation of Lithium Precipitation

[0184] Each electrode assembly of the above examples and comparative examples was placed in a pouch-type battery case made of PP / Al / nylon laminate sheet, an electrolyte was injected and sealed, and then an activation process was performed to manufacture a secondary battery.

[0185] After performing 200 charge-discharge cycles on the manufactured secondary battery, the battery was disassembled to visually check whether lithium had been deposited at the negative electrode, and the results are shown in Table 1. In Table 1, conditions 1, 2, and 3 are as previously described, "O" indicates that the condition is satisfied or lithium is deposited, and "X" indicates that the condition is not satisfied or lithium is not deposited.

[0186] Whether Condition 1 is satisfied Whether Condition 2 is satisfied Whether Condition 3 is satisfied Whether lithium precipitates Example 1 O O O X Example 2 O O O X Comparative Example 1 X X X O Comparative Example 2 X X X O

[0187] As described above, the electrode assembly manufactured by the method according to the embodiment of the present invention satisfies conditions 1, 2, and 3, and no lithium was deposited at the negative electrode after 200 cycles of charge-discharge. On the other hand, lithium deposition was observed in the secondary battery containing the electrode assembly of the comparative example after 200 cycles of charge-discharge.

[0188] As described above, according to the present invention, since a face-to-face position having a positive / negative thickness ratio satisfying conditions 1 to 3 is specified and a notching line is set based on this, local reversal of the NP Ratio can be easily prevented without changing the pre-set spacing between the positive and negative poles. Explanation of the symbols

[0190] 10: Anode sheet 11: Anode composite uncoated part 12: Anode mixture coating section 20: Cathode sheet 21: Cathode mixture uncoated part 22: Cathode mixture coating section 100: Electrode assembly 110: Anode, planned anode notching line 120: Cathode, planned cathode notching line 111: Positive tab 121: Cathode tab 111a: Bipolar shoulder line 111b: bipolar indeterminate region 121a: Cathode shoulder line 121b: Cathode-free region P1: Cathode first facing planned line P2: Cathode second facing planned line P3: Planned line for the first positive face P4: Planned line for the second bipolar face

Claims

Claim 1 An electrode assembly for a lithium secondary battery in which a positive electrode and a negative electrode face each other with a separator in between, wherein the protrusion direction of the positive electrode tab and the protrusion direction of the negative electrode tab are opposite to each other, wherein the negative electrode tab includes a negative electrode shoulder portion coated with a negative electrode composite on a negative electrode current collector and a negative electrode uncoated portion not coated with a negative electrode composite, wherein the negative electrode shoulder portion includes a negative electrode sliding region that forms an inclined surface on the plane of the negative electrode current collector as the thickness of the negative electrode composite layer decreases along the protrusion direction of the negative electrode tab, and the thickness T of the negative electrode composite layer at the central portion of the negative electrode NC Regarding the thickness T of the cathode composite layer at the first facing position where the cathode faces the lower part of the anode, the thickness T of the cathode composite layer at the first facing position where the cathode faces the lower part of the anode. N1 The first cathode thickness ratio RT, which is the ratio value of N1 (=T N1 / T NC ) and thickness T of the anode composite layer at the center of the anode PC Regarding the thickness T of the anode composite layer at the lower part of the anode, P1 The first anode thickness ratio RT, which is the ratio value of P1 (=T P1 / T PC ) is an electrode assembly characterized by satisfying the following condition 1. [Condition 1] RT N1 ≥(RT P1 / NP Ratio)×100.1(In ​​Condition 1 above, NP Ratio is a preset value representing the ratio of cathode capacity to anode capacity per unit area) Claim 2 In claim 1, the thickness T of the cathode composite layer at the central part of the cathode. NC Regarding the thickness T of the cathode composite layer at the second facing position where the cathode faces the upper part of the anode, the thickness T of the cathode composite layer at the second facing position where the cathode faces the upper part of the anode. N2 The ratio value of the cathode second thickness ratio RT N2 (=T N2 / T NC ) and thickness T of the anode composite layer at the center of the anode PC Regarding the thickness T of the anode composite layer at the upper part of the anode, P2 RT, the ratio value of the anode second thickness ratio P2 (=T P2 / T PC An electrode assembly characterized by satisfying the following condition 2. [Condition 2] RT N2 ≥(RT P2 / NP Ratio)×100.1(In ​​Condition 2 above, NP Ratio is a preset value, meaning the ratio of cathode capacity to anode capacity per unit area) Claim 3 An electrode assembly according to claim 1, characterized in that the ratio of the length L1 of the cathode shoulder line to the length L3 from the first facing position to the end portion of the cathode shoulder line is 0.5 to 0.

9. Claim 4 In claim 1, the first anode thickness ratio RT P1 (=T P1 / T PC ) is an electrode assembly characterized by being 0.6 to 1. Claim 5 In claim 2, the positive tab of the positive electrode comprises a positive shoulder portion coated with a positive composite on a positive current collector and a positive non-positive portion not coated with a positive composite, and the positive shoulder portion comprises a positive sliding region in which the thickness of the positive composite layer is reduced along the protruding direction of the positive tab to form an inclined surface on the plane of the positive current collector. Claim 6 A lithium secondary battery comprising one or more electrode assemblies according to claim 1. Claim 7 A process of preparing an electrode sheet comprising, on an electrode current collector sheet, an electrode mixture coated portion on which an electrode mixture is coated, and an electrode mixture non-coated portion located at least one edge of the electrode mixture coated portion, on which the electrode mixture is not coated; a thickness measurement process of measuring the thickness of each electrode mixture layer at a plurality of points selected at the boundary of the electrode mixture coated portion and the electrode mixture non-coated portion, and measuring the thickness of the electrode mixture layer at the center of the electrode mixture coated portion; an electrode thickness ratio calculation process of calculating ratio values ​​of the thickness of each electrode mixture layer at the plurality of points relative to the thickness of the electrode mixture layer at the center of the electrode mixture coated portion; a process of setting a positive / negative notching line, which sets a notching line to be notched in the form of an individual positive and a individual negative in the positive sheet and the negative sheet based on the calculated positive thickness ratio value and negative thickness ratio value; and a notching process of notching according to the set notching line. A method for manufacturing an electrode assembly comprising a lamination process in which a separator is interposed between a notched anode and a cathode and the electrode is laminated, wherein the process of setting the anode / cathode notching planned lines comprises: determining a first anode face planned line (P3) in an anode sheet and determining a first cathode face planned line (P1) in a cathode sheet; determining the first anode face planned line (P3) as a notching planned line for the anode lower portion; and determining a notching planned line for the cathode upper portion based on the first cathode face planned line (P1), wherein the first cathode face planned line (P1) and the first anode face planned line (P3) are determined such that the cathode thickness ratio in the first cathode face planned line (P1) and the anode thickness ratio in the first anode face planned line (P3) satisfy the following condition 3. [Condition 3] Cathode Thickness Ratio ≥ (Anode Thickness Ratio / NP Ratio) × 100.1 (In Condition 3 above, NP Ratio is a preset value representing the ratio of cathode capacity to anode capacity per unit area) Claim 8 In claim 7, the process of setting the positive / negative notching planned line further comprises the process of tabulating the combination of positive thickness ratio and negative thickness ratio satisfying condition 3 according to a preset NP Ratio value, a method for manufacturing an electrode assembly. Claim 9 A method for manufacturing an electrode assembly according to claim 7, wherein in the process of determining the notching planned line of the upper portion of the cathode, the notching planned line of the upper portion of the cathode is determined as a virtual line connecting points spaced apart by a planar spacing G1 between the anode and the cathode along the width direction of the cathode sheet from the first cathode face planned line. Claim 10 A method for manufacturing an electrode assembly according to claim 7, wherein the process of setting the positive / negative notching planned lines further includes the process of determining a second positive face planned line (P4) in the positive sheet and determining a second negative face planned line (P2) in the negative sheet, and wherein the second negative face planned line (P2) and the second positive face planned line (P4) are determined such that the ratio of the negative thickness in the second negative face planned line (P2) and the ratio of the positive thickness in the second positive face planned line (P4) satisfy condition 3. Claim 11 A method for manufacturing an electrode assembly according to claim 10, wherein the second cathode facing line (P2) is determined as a virtual line connecting points spaced apart from the first cathode facing line (P1) by a length C in the electric direction of the anode along the width direction of the cathode sheet. Claim 12 A method for manufacturing an electrode assembly according to claim 10, wherein the process of setting the positive / negative notching planned line further comprises: the process of determining the positive second facing planned line (P4) as the notching planned line of the upper part of the positive electrode; and the process of determining a virtual line connecting points spaced apart by a length A in the electric direction of the negative electrode along the width direction of the negative electrode sheet from the notching planned line of the upper part of the negative electrode as the notching planned line of the lower part of the negative electrode. Claim 13 In claim 7, the process of setting the positive / negative notching planned lines further includes the process of determining the positive tab notching planned line and the negative tab notching planned line, and the process of determining the positive tab notching planned line and the negative tab notching planned line is characterized by setting the positive tab notching planned line so as to include a positive shoulder line portion coated with a positive agent within the positive tab, and setting the negative tab notching planned line so as to include a negative shoulder line portion coated with a negative agent within the negative tab. Claim 14 A method for manufacturing an electrode assembly according to claim 7, wherein the lamination process comprises laminating the anodes such that the anode lower portion notching line of the notched anode is positioned on the first face-planning line of the notched cathode. Claim 15 A method for manufacturing an electrode assembly according to claim 7, wherein the lamination process comprises laminating the anodes such that the anode upper portion notching line of the notched anode is positioned on the second face-planning line of the notched cathode. Claim 16 A method for managing the sliding specifications of an electrode including a sliding region in which the thickness of the electrode composite layer gradually decreases to form an inclined surface with respect to the current collector plane, wherein the thickness T of the anode composite layer in the anode center portion of the anode sheet PC and thickness T of the anode composite layer at the planned lower portion of the anode P1 Measure each, and the above T PC T for P1 The first anode thickness ratio RT, which is the ratio value of P1 (=T P1 / T PC A process for calculating ); a process for determining a first cathode facing line (P1) to face the anode lower portion planned portion in the cathode sheet; and a process for determining the thickness T of the cathode composite layer in the cathode central portion in the cathode sheet. NC and the thickness T of the cathode composite layer at the first cathode face planned line (P1) above. N1 Measure each, and the above T NC The above T regarding N1 The first cathode thickness ratio RT, which is the ratio value of N1 (=T N1 / T NC A process for calculating ); and the first anode thickness ratio RT P1 and the first cathode thickness ratio RT N1 A method for managing electrode sliding specifications that includes a process for verifying whether the relationship satisfies the following Condition 1. [Condition 1] RT N1 ≥(RT P1 / NP Ratio)×100.1(In ​​Condition 1 above, NP Ratio is a preset value representing the ratio of cathode capacity to anode capacity per unit area) Claim 17 In claim 16, the thickness T of the anode composite layer at the planned upper portion of the anode P2 Measure and the above T PC The above T regarding P2 The second anode thickness ratio RT, which is the ratio value of P2 (=T P2 / T PC A process for calculating ); a process for determining a second cathode facing line (P2) to face the upper part of the anode in the cathode sheet; and a process for determining the thickness T of the cathode composite layer at the second cathode facing line (P2). N2 Measure and the above T NC The above T regarding N2 The second cathode thickness ratio RT, which is the ratio value of N2 (=T N2 / T NC A process for calculating ); and the second anode thickness ratio RT P2 and the second cathode thickness ratio RT N2 A method for managing electrode sliding specifications that further includes a process for verifying whether the relationship satisfies Condition 2 below. [Condition 2] RT N2 ≥(RT P2 / NP Ratio)×100.1(In ​​Condition 2 above, NP Ratio is a preset value, meaning the ratio of cathode capacity to anode capacity per unit area) Claim 18 A method for managing electrode sliding specifications according to claim 16, wherein in the process of determining the first cathode face-to-face line, the first cathode face-to-face line (P1) is determined as a virtual line connecting points spaced apart along the width direction by the length L1 of the cathode shoulder line and the plane-side spacing G1 between the anode and the cathode from the boundary line between the cathode composite coating part and the cathode composite non-coating part. Claim 19 A method for managing electrode sliding specifications according to claim 17, wherein in the process of determining the second cathode facing line, the second cathode facing line (P2) is determined as a virtual line connecting points spaced apart from the first cathode facing line (P1) by a length C in the electric direction of the anode along the width direction.

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