Method for evaluating insulation of a covered portion

Abstract

The present invention relates to a method for evaluating the insulation of a covering portion, and the method includes: (a) a process of applying an insulating coating liquid onto an electrode mixture layer and drying it to simulate the covering portion, and collecting data on the length c of the gap of the applicator, the thickness d increased by the insulating coating, and the capacitance f of the covering portion; (b) a process of applying an insulating coating liquid onto a current collector and drying it to simulate a pure insulating coating layer, and collecting data on the length g of the gap of the applicator and the thickness h of the pure insulating coating layer; (c) a process of generating a relational expression 1 between the thickness H of the pure insulating coating layer and the capacitance F of the covering portion based on the data collected in processes (a) and (b); (d) a process of measuring the thickness of the pure insulating coating layer at the electrode for evaluation; and (e) a process of calculating the capacitance of the covering portion by substituting the thickness of the pure insulating coating layer measured in process (d) into the relational expression 1.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0153807, filed on November 17, 2020, and the entire contents of the Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method for evaluating the insulation of an insulating coating layer, and more particularly, to a method for evaluating the insulation of a covering portion without measuring the thickness of the insulating coating layer in the covering portion when the insulating coating layer is laminated on an electrode mixture layer. Background Art

[0003] With the development of technology and the increasing demand for mobile devices, the demand for batteries as an energy source is rapidly increasing. Among such secondary batteries, many studies have been conducted on lithium secondary batteries having high energy density and discharge voltage, and lithium secondary batteries have been commercialized and widely used.

[0004] When such a lithium secondary battery is exposed to high temperature, there is a possibility of short circuit due to contact between the positive electrode and the negative electrode. In addition, even when a large current flows in a short period of time due to overcharging, external short circuit, nail penetration, local crushing, etc., there is a risk of fire / explosion because the battery is heated due to heat generation.

[0005] Such a phenomenon generally occurs at the end of the electrode active material applied on the electrode current collector during electrode lamination, and various methods have been tried to reduce the possibility of short circuit of the electrode under external shock or high temperature.

[0006] Figure 1 The process of applying an insulating coating liquid on the end of the positive electrode mixture coating portion to prevent short circuit between the positive electrode and the negative electrode is shown. Refer to Figure 1 , an electrode mixture layer 12 is formed by coating an electrode slurry including an electrode active material on an electrode current collector 11, and the insulating coating liquid is applied on the uncoated portion around the end of the electrode mixture layer 12 and dried to form insulating coating layers 13a and 13b. Since the electrode mixture layer before drying has fluidity, a sliding phenomenon is shown, in which the thickness of the end gradually decreases. In addition, since the insulating coating liquid is a fluid, the insulating coating liquid is applied not only on the uncoated portion but also on the sliding portion of the electrode mixture layer. Therefore, the finally formed insulating coating layer includes a pure insulating coating layer 13b formed on the uncoated portion and a covering portion insulating coating layer 13a formed on the electrode mixture layer.

[0007] In Figure 1In the electrode shown, the pure insulating coating layer blocks the movement of electrons to prevent short - circuiting between the positive and negative electrodes, and the covered part of the insulating coating layer restricts the movement of lithium ions to non - existent places, thereby further improving the safety of the battery.

[0008] In addition, since the insulation of the insulating coating layer is proportional to the thickness of the insulating coating layer, the insulation performance is managed by measuring the thickness of the insulating coating layer. In an electrode with a covered part, it is easy to measure the thickness of the pure insulating coating layer 13b that has been coated, but in order to separately measure the thickness of the insulating coating layer 13a of the covered part, new equipment should be introduced, which may take a lot of time and cost. In addition, in the insulating coating layer of the covered part, different from the pure insulating coating layer, part of the insulating coating liquid penetrates into the pores of the electrode mixture layer. Therefore, the insulation performance of the covered part is shown by the combined effect of both the insulating material of the insulating coating layer and the insulating material that penetrates into the electrode mixture layer. Therefore, it is difficult to evaluate the insulation by measuring the thickness of the insulating coating layer of the covered part.

[0009] Therefore, a technique is needed to predict the insulation of the covered part using conventional management factors without introducing new equipment. Summary of the Invention

[0010]

Technical Problem

[0011] The present invention is considered to solve at least some of the above problems. For example, an aspect of the present invention provides a method for evaluating the insulation of the insulating coating layer in the covered part without introducing new equipment.

[0012]

Technical Solution

[0013] The method for evaluating insulation of the present invention for solving the above problems includes:

[0014] (a) A process of applying an insulating coating liquid on the electrode mixture layer and drying it to simulate the covered part, and collecting data on the length c of the gap of the applicator, the thickness d increased by the insulating coating, and the capacity f of the covered part;

[0015] (b) A process of applying an insulating coating liquid on the current collector and drying it to simulate the pure insulating coating layer, and collecting data on the length g of the gap of the applicator and the thickness h of the pure insulating coating layer;

[0016] (c) A process of generating a relational expression 1 between the thickness H of the pure insulating coating layer and the capacity F of the covered part based on the data collected through processes (a) and (b);

[0017] (d) A process of measuring the thickness of the pure insulating coating layer at the electrode for evaluation; and

[0018] (e) A process of calculating the capacitance of the covered portion by substituting the thickness of the pure insulating coating layer measured in process (d) into Equation 1.

[0019] In a specific example, process (c) includes:

[0020] (c-1) A process of deriving Equation 2 between the thickness D increased by the insulating coating and the capacitance F of the covered portion based on the data of the capacitance f of the covered portion according to the thickness d increased by the insulating coating, which was collected during process (a);

[0021] (c-2) A process of deriving Equation 3 between the thickness D increased by the insulating coating and the thickness H of the pure insulating coating layer based on the data of the length c of the gap of the applicator and the thickness d increased by the insulating coating collected during process (a), and the data of the length g of the gap of the applicator and the thickness h of the pure insulating coating layer collected during process (b); and

[0022] (c-3) A process of deriving Equation 1 through the combination of Equation 2 and Equation 3.

[0023] In a specific example, process (a) includes:

[0024] (a-1) A process of applying an insulating coating liquid on the electrode mixture layer and drying it to simulate the covered portion, and measuring the length c of the gap of the applicator for applying the insulating coating liquid;

[0025] (a-2) A process of measuring the thickness d increased by the insulating coating in the simulated covered portion; and

[0026] (a-3) A process of measuring the capacitance f of the simulated covered portion.

[0027] In this article, the data of the length c of the gap of the applicator, the thickness d increased by the insulating coating, and the capacitance f of the covered portion are collected by repeating processes (a-1) to (a-3).

[0028] In a specific example, process (b) includes:

[0029] (b-1) A process of applying an insulating coating liquid on the current collector and drying it to simulate the pure insulating coating layer, and measuring the length g of the gap of the applicator for applying the insulating coating liquid; and

[0030] (b-2) A process of measuring the thickness h of the pure insulating coating layer simulated by process (b-1).

[0031] In this text, data on the length g of the gap of the applicator for applying the insulating coating liquid and the thickness h of the pure insulating coating layer are collected by repeating processes (b-1) to (b-2).

[0032] In a specific example, process (c-2) includes:

[0033] (c-2-1) A process of deriving the relational expression 4 between the length C of the gap of the applicator and the thickness D increased by the insulating coating based on the data on the length c of the gap of the applicator and the thickness d increased by the insulating coating collected during process (a);

[0034] (c-2-2) A process of deriving the relational expression 5 between the length G of the gap of the applicator and the thickness H of the pure insulating coating layer based on the data on the length g of the gap of the applicator and the thickness h of the pure insulating coating layer collected during process (b); and

[0035] (c-2-3) A process of deriving the relational expression 3 between the thickness D increased by the insulating coating and the thickness H of the pure insulating coating layer by eliminating the gap of the applicator as a parameter through the combination of relational expression 4 and relational expression 5.

[0036] In a specific example, process (a-3) includes the process of manufacturing a button cell including the simulated covering portion and measuring the capacity f of the covering portion by measuring the charge capacity or discharge capacity of the button cell, and the button cell can be a half cell.

[0037] In a specific example, during the simulation of the covering portion in process (a), a part of the insulating coating liquid applied on the electrode mixture layer penetrates into the electrode mixture layer.

[0038] In a specific example, the thickness d increased by the insulating coating is obtained by subtracting the thickness of the electrode mixture layer before applying the insulating coating liquid from the total thickness of the electrode mixture layer and the insulating coating layer after drying the insulating coating liquid.

[0039] In a specific example, the insulating coating layer includes polyvinylidene fluoride (PVDF).

[0040] In a specific example, the electrode is a positive electrode.

[0041] In a specific example, the thickness of the pure insulating coating layer is equal to or less than 15 μm.

[0042]

Beneficial effects

[0043] According to the present invention, the insulation of the covering portion can be easily evaluated by measuring the thickness of a pure insulation coating layer whose thickness can be easily measured, and the insulation evaluation result is also relatively accurate by reflecting the insulation performance of the insulation material penetrating into the electrode mixture layer in the covering portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic diagram showing a process of applying an insulation coating liquid to an end portion of a positive electrode mixture coating portion.

[0045] Figure 2 is a flowchart illustrating a process for evaluating the insulation of a covering portion according to an embodiment of the present invention.

[0046] Figure 3 is a flowchart illustrating a process (c) for deriving Relational Expression 1 according to an embodiment of the present invention.

[0047] Figure 4 is a schematic diagram illustrating a process (a) for simulating a covering portion and collecting data according to an embodiment of the present invention.

[0048] Figure 5 is a schematic diagram illustrating a process (b) for simulating a pure insulation coating layer and collecting data according to an embodiment of the present invention.

[0049] Figure 6 is a flowchart illustrating a detailed process of process (a) according to an embodiment of the present invention.

[0050] Figure 7 is a flowchart illustrating a detailed process of process (b) according to an embodiment of the present invention.

[0051] Figure 8 is a flowchart illustrating a detailed process of process (c-2) for deriving Relational Expression 3 according to an embodiment of the present invention.

[0052] Figure 9 is a graph showing Relational Expression 4 and Relational Expression 5 according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The terms and words used in this specification and the claims should not be construed as limited to ordinary or dictionary terms, and the present inventor may appropriately define the concept of the terms in order to best describe his invention. The terms and words should be construed as having meanings and concepts consistent with the technical idea of the present invention.

[0054] In the present application, it should be understood that terms such as "including" or "having" are intended to indicate features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and they do not preclude the possibility of the presence or addition of one or more other features or numbers, steps, operations, components, parts, or combinations thereof. Additionally, when a part such as a layer, film, region, plate, etc. is referred to as being "on" another part, this includes not only the case where the part is "directly on" the other part, but also the case where another part is interposed therebetween. On the other hand, when a part such as a layer, film, region, plate, etc. is referred to as being "under" another part, this includes not only the case where the part is "directly under" the other part, but also the case where another part is interposed therebetween. Additionally, being arranged "on..." in the present application can include the cases of being arranged at the bottom as well as at the top.

[0055] In addition, in the present invention, the covered portion means a partial electrode portion in which an insulating coating layer has been formed on the electrode mixture layer included in the electrode including the insulating coating layer.

[0056] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0057] The present invention relates to a method for evaluating the insulation in a covered portion in the case where an insulating coating layer has been laminated on a sliding portion of an electrode mixture layer, and more particularly, to a new method for evaluating the insulation in the covered portion by measuring the thickness of the insulating coating layer (hereinafter referred to as "pure insulating coating layer") coated on an uncoated portion, because it is difficult to measure the thickness of the insulating coating layer in the covered portion.

[0058] In the specification of the present invention, the sliding portion has the concept of an inclined region including the end of the electrode mixture layer formed by the fluidity of the electrode paste and its periphery.

[0059] In the present invention, there is no limitation on the type of insulating material included in the insulating coating liquid for forming the insulating coating layer, as long as it exhibits an insulating effect. The insulating material may be at least one selected from the group consisting of polybutadiene, polyurethane, polyimide, acetate, polyester, polyphenylene sulfide (PPS), polystyrene, styrene-butadiene copolymer, (meth)acrylic copolymer, (meth)acrylate copolymer, polyacrylonitrile, polyvinyl chloride, polyfluorinated compound, polyvinyl alcohol, and polycyanoacrylate. In an example of the present invention, polyvinylidene fluoride (PVDF) is included in the insulating material.

[0060] The insulating coating layer can be formed over an area including the end of the electrode mixture layer to the uncoated portion of the active material and can be formed to have a thickness equal to or less than 15 μm and specifically in the range of 2 to 15 μm. When the thickness of the insulating coating layer is less than 2 μm, the effect of preventing the deintercalation of the active material or suppressing the movement of lithium ions becomes insignificant, and when the thickness of the insulating coating layer exceeds 15 μm, cracks may be generated on the active material layer due to the step difference in thickness.

[0061] The insulating coating layer is usually formed on the positive electrode, and the method for evaluating the insulation of the present invention can be applied to the positive electrode.

[0062] Figure 2 is a flowchart showing the process of the method for evaluating the insulation of the covering portion according to an embodiment of the present invention. Refer to Figure 2 , the method for evaluating the insulation of the covering portion according to the present invention includes: (a) a process of applying an insulating coating liquid on the electrode mixture layer and drying it to simulate the covering portion, and collecting data on the length c of the gap of the applicator, the thickness d increased by the insulating coating, and the capacity f of the covering portion;

[0063] (b) a process of applying an insulating coating liquid on the current collector and drying it to simulate a pure insulating coating layer, and collecting data on the length g of the gap of the applicator and the thickness h of the pure insulating coating layer;

[0064] (c) a process of generating a relational expression 1 between the thickness H of the pure insulating coating layer and the capacity F of the covering portion based on the data collected in processes (a) and (b);

[0065] (d) a process of measuring the thickness of the pure insulating coating layer at the electrode for evaluation; and

[0066] (e) a process of calculating the capacity of the covering portion by substituting the thickness of the pure insulating coating layer measured in process (d) into relational expression 1.

[0067] Similarly, according to the present invention, the insulation of the covering portion can be evaluated by measuring the thickness of the pure insulating coating layer and substituting the measured thickness of the pure insulating coating layer into relational expression 1. Therefore, there is no need to introduce new equipment to measure the thickness of the insulating coating layer in the covering portion, and there is no error in measuring the thickness of the insulating coating layer in the covering portion.

[0068] Hereinafter, the process of deriving relational expression 1 will be described in detail.

[0069] Figure 3 is a flowchart showing the process of process (c) of deriving relational expression 1 according to an embodiment of the present invention. Refer to Figure 3 , the process of deriving relational expression 1 includes:

[0070] (c-1) Process of deriving relationship 2 between the thickness D increased by the insulation coating and the capacity F of the covering part based on the data of the capacity f of the covering part according to the thickness d increased by the insulation coating collected during process (a);

[0071] (c-2) Process of deriving relationship 3 between the thickness D increased by the insulation coating and the thickness H of the pure insulation coating layer based on the data of the length c of the gap of the applicator and the thickness d increased by the insulation coating collected during process (a) and the data of the length g of the gap of the applicator and the thickness h of the pure insulation coating layer collected during process (b); and

[0072] (c-3) Process of deriving relationship 1 through the combination of relationship 2 and relationship 3.

[0073] In the present invention, in order to derive relationship 2 between the thickness D increased by the insulation coating and the capacity F of the covering part, and relationship 3 between the thickness D increased by the insulation coating and the thickness H of the pure insulation coating layer in the covering part, the covering part simulation process of process (a) and the pure insulation coating layer simulation process of process (b) are performed, and the data necessary for deriving relationship 2 and relationship 3 are collected through the two simulation processes.

[0074] Hereinafter, the process of deriving relationship 2 and relationship 3 through the two simulation processes will be described.

[0075] In the present invention, in order to evaluate the insulation in the covering part, the thickness of the insulation coating layer is not measured, but the insulation of the covering part is evaluated by measuring the thickness of the pure insulation coating layer. Therefore, in the present invention, two simulation processes of simulating the covering part and simulating the pure insulation coating layer are performed. Therefore, process (a) of simulating the covering part will be described first, and then process (b) of simulating the pure insulation coating layer will be described.

[0076] <Process (a) of simulating the covering part and collecting data>

[0077] Figure 4 is a schematic diagram of the process of simulating process (a) of the covering part. Refer to Figure 4 , an electrode paste including an electrode active material is coated on the current collector 11, and then an insulation coating liquid S is coated on the electrode mixture layer 12. At this time, the gap c of the applicator for applying the insulation coating liquid is measured, and the measured value is saved as c 1 , c 2 , c 3 , c 4 ....c nThereafter, if a drying process is performed, a covered portion is simulated as an insulating coating layer 13a is formed on the electrode mixture layer.

[0078] As described above, in the covered portion of the electrode, a part of the elements of the insulating coating liquid penetrates into the pores of the electrode mixture layer. Therefore, the insulation of the covered portion is also shown by the insulating coating liquid penetrating into the electrode mixture layer. Therefore, in order to ensure reliability, the data obtained by simulating the covered portion is necessary.

[0079] Reference Figure 4 , the coating thickness of the insulating coating liquid before the drying process is I, and the thickness decreases and becomes e after the drying process. This occurs as the solvent of the insulating coating liquid is removed and a part of the elements of the insulating coating liquid penetrates into the pores of the electrode mixture layer. Therefore, the insulation in the covered portion is shown by the elements of the insulating coating liquid present in the electrode mixture layer together with the insulating coating layer distinguishable by the naked eye.

[0080] Reference Figure 4 , after applying and drying the insulating coating liquid, the thickness of the electrode mixture layer slightly increases due to the insulating coating elements present in the electrode mixture layer. Therefore, in the present invention, in the simulated covered portion, after drying the insulating coating liquid, the increase in both the thickness of the electrode mixture layer and the final thickness e of the insulating coating layer shows the insulation, and thus includes a process of collecting data on the thickness d increased by the insulating coating.

[0081] The thickness d increased by the insulating coating is obtained by subtracting the thickness of the electrode mixture layer before applying the insulating coating liquid from the total thickness of the electrode mixture layer and the insulating coating layer after drying the insulating coating liquid.

[0082] Similarly, in process (a) of the present invention, the covered portion is simulated, and the thickness d increased by the insulating coating is considered to be a part of the insulation shown by the insulating coating layer, and a process of measuring the thickness d and the capacitance f of the covered portion is performed. The capacitance f is measured to measure the insulation.

[0083] Figure 6 is a flowchart illustrating the detailed process of process (a) according to an embodiment of the present invention. Reference Figure 6 , process (a) according to an embodiment of the present invention includes:

[0084] (a-1) A process of applying and drying an insulating coating liquid on the electrode mixture layer to thereby simulate a covered portion and measuring the length c of the gap of the applicator for applying the insulating coating liquid;

[0085] (a-2) Process of measuring the increased thickness d by the insulating coating in the simulated covering portion; and

[0086] (a-3) Process of measuring the capacitance f of the simulated covering portion.

[0087] In this text, data on the length c of the gap of the applicator, the increased thickness d by the insulating coating, and the capacitance f of the covering portion are collected by repeating processes (a-1) to (a-3).

[0088] In process (a-1), c is collected by measuring the gap c of the applicator 1 、c 2 、c 3 、c 4 ...c n 's data, and in process (a-2), d is collected by measuring the increased thickness d by the insulating coating 1 、d 2 、d 3 、d 4 ...d n 's data, and in process (a-3), f is collected by measuring the capacitance f of the covering portion 1 、f 2 、f 3 、f 4 ...f n 's data.

[0089] In an embodiment of the present invention, process (a-3) includes the process of manufacturing a button battery including the simulated covering portion and measuring the capacitance f of the covering portion by measuring the charging capacitance or discharging capacitance of the button battery. At this time, the button battery may be a half-cell.

[0090] When generating relational expressions 2 and 4, the data collected by repeating processes (a-1) to (a-3) is used as reference data.

[0091] <Process (b) of simulating a pure insulating coating layer and collecting data>

[0092] Figure 5 is a schematic diagram showing the process of simulating a pure insulating coating layer process (b) according to an embodiment of the present invention and collecting data. Refer to Figure 5 , a pure insulating coating layer 13b is simulated by applying an insulating coating liquid S on the current collector 11 and drying the insulating coating liquid S.

[0093] Figure 7 is a flowchart showing the detailed process of process (b) according to an embodiment of the present invention. Refer to Figure 7 , process (b) according to an embodiment of the present invention includes:

[0094] (b-1) A process of applying an insulating coating liquid onto a current collector and drying it to simulate a pure insulating coating layer, and measuring the length g of the gap of the applicator for applying the insulating coating liquid; and

[0095] (b-2) A process of measuring the thickness h of the pure insulating coating layer simulated by the process (b-1).

[0096] In this text, data on the length g of the gap of the applicator for applying the insulating coating liquid and the thickness h of the pure insulating coating layer are collected by repeating the processes (b-1) to (b-2).

[0097] In the process (b-1), g is collected by measuring the length g of the gap of the applicator for applying the insulating coating liquid 1 、g 2 、g 3 、g 4 ...g n 's data, and in the process (b-2), h is collected by measuring the thickness h of the pure insulating coating layer corresponding to g 1 、h 2 、h 3 、h 4 ...h n 's data.

[0098] When generating the relational expression 5 to be described later, the data collected by repeating the processes (b-1) to (b-2) is used as reference data.

[0099] <Process (c-1) for deriving relational expression 2>

[0100] The process (c-1) of the present invention is a process of deriving the relational expression 2 between the thickness D increased by the insulating coating and the capacitance F of the covered portion. This is generated based on the thickness d increased by the insulating coating and the corresponding capacitance f of the covered portion collected in the process (a). That is, the relational expression 2 is derived by analyzing the correlation between d and the corresponding capacitance f.

[0101] <Process (c-2) for deriving relational expression 3>

[0102] Figure 8 is a flowchart illustrating the detailed process of the process (c-2) for deriving the relational expression 3 according to an embodiment of the present invention. Refer to Figure 8 this, the process (c-2) of deriving the relational expression 3 of the present invention includes:

[0103] (c-2-1) The process of deriving the relationship 4 between the length C of the gap of the applicator and the thickness D increased by the insulation coating based on the data collected during process (a) regarding the length c of the gap of the applicator and the thickness d increased by the insulation coating;

[0104] (c-2-2) The process of deriving the relationship 5 between the length G of the gap of the applicator and the thickness H of the pure insulation coating layer based on the data collected during process (b) regarding the length g of the gap of the applicator and the thickness h of the pure insulation coating layer; and

[0105] (c-2-3) The process of deriving the relationship 3 between the thickness D increased by the insulation coating and the thickness H of the pure insulation coating layer by eliminating the gap of the applicator as a parameter through the combination of relationship 4 and relationship 5.

[0106] (c-2-1)'s relationship 4 is generated from the data regarding the length c of the gap of the applicator collected during process (a) and the data regarding the thickness d increased by the insulation coating based thereon. That is, relationship 4 is derived by analyzing the correlation between c and the corresponding d.

[0107] (c-2-2)'s relationship 5 is generated from the data regarding the length g of the gap of the applicator collected during process (b) and the data regarding the thickness d of the pure insulation coating layer based thereon. That is, relationship 5 is derived by analyzing the correlation between g and the corresponding h.

[0108] (c-2-3)'s process of generating relationship 3 is a process of deriving the relationship 3 between the thickness D increased by the insulation coating and the thickness H of the pure insulation coating layer by combining the above-generated relationship 4 and relationship 5 and eliminating the lengths c and g of the gap of the applicator that are common parameters of these equations.

[0109] <The process of deriving relationship 1 <c-3>>

[0110] The above-mentioned relational expression 2 is the relational expression between the thickness D increased by the insulation coating and the capacitance F of the covering portion, and the relational expression 3 is the relational expression between the thickness D increased by the insulation coating and the thickness H of the pure insulation coating layer. When these two expressions are combined, the common parameter D can be eliminated. Therefore, the relational expression 1 between the thickness H of the pure insulation coating layer and the capacitance F of the covering portion is generated.

[0111] In the evaluation method of the present invention, when evaluating the insulation of the covering portion in the electrode including the covering portion, the capacitance F of the covering portion can be calculated by measuring the thickness of the pure insulation coating layer and substituting the measured thickness of the pure insulation coating layer into the relational expression 1, and the insulation can be evaluated by the capacitance F. Therefore, the insulation of the covering portion can be easily evaluated, and the insulation evaluated in this way can be ensured.

[0112] Hereinafter, embodiments of the present invention will be described, but the following embodiments are for illustrating the present invention, and the scope of the present invention is not limited solely to these embodiments.

[0113] Example: Derivation relation 1

[0114] <Process (a) of simulating the covering portion and collecting data>

[0115] The positive electrode paste is manufactured by mixing a positive electrode active material containing nickel, manganese, and chromium in a ratio of 7:1:2, carbon black as a conductive material, and carbon black as a binder in a weight ratio of 97:1.5 and 1.5, and dispersing the mixture in an NMP solvent. The electrode mixture layer is manufactured by applying the positive electrode paste on an aluminum current collector and drying the positive electrode paste. Thereafter, the simulation of the covering portion is completed by applying an insulation coating liquid of 10 μm or less including PVDF and drying the insulation coating liquid at a temperature of 130 °C for 20 minutes.

[0116] At this time, data is collected by measuring the length c of the gap of the applicator for applying the insulation coating liquid, the corresponding thickness d increased by the insulation coating, and the capacitance f of the covering portion, and then repeating this process while changing c.

[0117] When measuring the capacitance f, a button half-cell is manufactured using the positive electrode including the simulated covering portion and a lithium counter electrode, and charge / discharge is performed, and then the discharge capacitance f is measured.

[0118] <Process (b) of simulating the pure insulation coating layer and collecting data>

[0119] An insulating coating liquid is applied to the aluminum current collector, and the length g of the gap of the applicator is adjusted using the same aluminum current collector and insulating coating liquid as in the simulation of the covering portion. The applied insulating coating liquid is dried at 130 °C for 20 minutes to simulate a pure insulating coating layer.

[0120] At this time, data is collected by measuring the length g of the gap of the applicator for applying the insulating coating liquid and the thickness h of the pure insulating coating layer, and then repeating the process while changing g.

[0121] <Process of deriving relational expression 2 (c-1)>

[0122] Relational expression 2 between the thickness D increased by the insulating coating and the capacitance F of the covering portion is generated from the data d and f collected during process (a), and the generated relational expression 2 is as follows.

[0123] The derived relational expression 2 is as follows.

[0124] [Relational expression 2]

[0125] F = 0.37894 - 4.7 * 10^26 * exp(-68.984 * D) - 2.91 * 10^2 * exp(-1.21385 * D)

[0126] <Process of deriving relational expression 3 (c-2)>

[0127] Relational expression 3 is derived by performing process (c-2-1) of deriving relational expression 4 between the gap C of the applicator and the thickness D increased by the insulating coating, and process (c-2-2) of deriving relational expression 5 between the length G of the gap of the applicator and the thickness H of the pure insulating coating layer.

[0128] Relational expression 4 is derived by analyzing the data c and d collected during process (a), and the derived relational expression 4 is shown in Figure 9 and is as follows.

[0129] [Relational expression 4]

[0130] D = 0.0566C - 1.2553

[0131] Relational expression 5 is derived by analyzing the data g and h collected during process (b), and the derived relational expression 5 is shown in Figure 9 and is as follows.

[0132] [Relational expression 5]

[0133] H = 0.0417G - 1.5335

[0134] The relational expression 3 between the increased thickness D by the insulation coating and the thickness H of the pure insulation coating layer is derived by the combination of the derived relational expressions 4 and 5. Specifically, in the derived relational expressions 4 (D = 0.0566C - 1.2553) and 5 (H = 0.0417G - 1.5335), both C and G are the lengths of the gap of the applicator of the insulation coating liquid. Therefore, the relational expression 3 between the thickness H of the pure insulation coating layer and the increased thickness D by the insulation coating is derived using C and G as parameters, and the relational expression 3 is as follows.

[0135] [Relational Expression 3]

[0136] H = 0.736749D - 0.610353

[0137] <Process of Deriving Relational Expression 1 <c-3>>

[0138] The relationship 1 between the thickness H of the pure insulating coating layer and the capacitance F of the covered portion can be obtained by combining relationship 3 and relationship 2. Specifically, relationship 1 is obtained by eliminating the common parameter D through the combination of relationship 3 and relationship 2, and relationship 1 is as follows.

[0139] [Relationship 1]

[0140] F = 177.93131 + (-71.22543) * (1 - exp(-H / 0.01068)) + (-106.32694) * (1 - exp(-H / 0.60695))

[0141] The insulation of the covered portion can be evaluated by measuring the thickness of the pure insulating coating layer and substituting the measured thickness into relationship 1.

[0142] [Description of Reference Numerals]

[0143] 11: Current collector

[0144] 12: Electrode mixture layer

[0145] 13: Insulating coating layer

[0146] 13a: Insulating coating layer of the covered portion

[0147] 13b: Pure insulating coating layer

[0148] S: Insulating coating liquid

Claims

1. A method for evaluating the insulation of a covered portion when an insulating coating layer has been laminated on a sliding portion of an electrode mixture layer, wherein, the sliding portion includes an inclined region at an end of the electrode mixture layer formed by fluidity and its periphery, the covered portion is a partial electrode portion of the electrode on which the insulating coating layer has been formed in the electrode including the insulating coating layer, and the method includes: (a) A process of applying an insulating coating liquid on the electrode mixture layer and drying it to simulate the covered portion, and collecting data on the length c of the gap of the applicator, the thickness d increased by the insulating coating, and the charging or discharging capacity f of the covered portion; (b) A process of applying an insulating coating liquid on a current collector and drying it to form a pure insulating coating layer, and collecting data on the length g of the gap of the applicator and the thickness h of the pure insulating coating layer; (c) A process of generating a relational expression 1 between the thickness H of the pure insulating coating layer and the charging or discharging capacity F of the covered portion based on the data collected through processes (a) and (b); (d) A process of measuring the thickness of the pure insulating coating layer at the electrode for evaluation; and (e) A process of calculating the charging or discharging capacity of the covered portion by substituting the thickness of the pure insulating coating layer measured in process (d) into the relational expression 1, wherein, process (c) includes: (c-1) A process of deriving a relational expression 2 between the thickness D increased by the insulating coating and the charging or discharging capacity F of the covered portion based on the data on the charging or discharging capacity f of the covered portion according to the thickness d increased by the insulating coating collected during process (a); (c-2) A process of deriving a relational expression 3 between the thickness D increased by the insulating coating and the thickness H of the pure insulating coating layer based on the data on the length c of the gap of the applicator and the thickness d increased by the insulating coating collected during process (a) and the data on the length g of the gap of the applicator and the thickness h of the pure insulating coating layer collected during process (b); and (c-3) A process of deriving the relational expression 1 through the combination of the relational expression 2 and the relational expression 3.

2. The method according to claim 1, wherein, process (a) includes: (a-1) A process of applying an insulating coating liquid on the electrode mixture layer and drying it to simulate the covered portion, and measuring the length c of the gap of the applicator for applying the insulating coating liquid; (a-2) A process of measuring the thickness d increased by the insulating coating in the simulated covered portion; and (a-3) A process of measuring the charging or discharging capacity f of the simulated covered portion, wherein the data on the length c of the gap of the applicator, the thickness d increased by the insulating coating, and the charging or discharging capacity f of the covered portion are collected by repeating processes (a-1) to (a-3).

3. The method according to claim 1, wherein, Process (b) includes: (b-1) a process of applying an insulating coating liquid onto the current collector and drying it to form the pure insulating coating layer, and measuring the length g of the gap of the applicator that applies the insulating coating liquid; and (b-2) a process of measuring the thickness h of the pure insulating coating layer formed through process (b-1), wherein data on the length g of the gap of the applicator that applies the insulating coating liquid and the thickness h of the pure insulating coating layer are collected by repeating processes (b-1) to (b-2).

4. The method according to claim 1, wherein, Process (c-2) includes: (c-2-1) a process of deriving relational expression 4 between the length C of the gap of the applicator and the thickness D increased through insulating coating based on data on the length c of the gap of the applicator and the thickness d increased through insulating coating collected during process (a); (c-2-2) a process of deriving relational expression 5 between the length G of the gap of the applicator and the thickness H of the pure insulating coating layer based on data on the length g of the gap of the applicator and the thickness h of the pure insulating coating layer collected during process (b); and (c-2-3) a process of deriving relational expression 3 between the thickness D increased through insulating coating and the thickness H of the pure insulating coating layer by eliminating the gap of the applicator as a parameter through the combination of relational expression 4 and relational expression 5.

5. The method according to claim 2, wherein, Process (a-3) includes manufacturing a button cell including the simulated covering portion, and measuring the charging or discharging capacity f of the covering portion by measuring the charging capacity or discharging capacity of the button cell.

6. The method according to claim 5, wherein, The button cell is a half cell.

7. The method according to claim 1, wherein, During the simulation of the covering portion in process (a), a part of the insulating coating liquid applied onto the electrode mixture layer penetrates into the electrode mixture layer.

8. The method according to claim 1, wherein, The thickness d increased through insulating coating is obtained by subtracting the thickness of the electrode mixture layer before applying the insulating coating liquid from the total thickness of the electrode mixture layer and the insulating coating layer after drying the insulating coating liquid.

9. The method according to claim 1, wherein, The insulating coating layer includes polyvinylidene fluoride (PVDF).

10. The method according to claim 1, wherein, The electrode is a positive electrode.

11. The method according to claim 1, wherein, The thickness of the pure insulating coating layer is equal to or less than 15 μm.

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