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EP-4099425-B1 - METHOD FOR EVALUATING INSULATION OF OVERLAY PART

EP4099425B1EP 4099425 B1EP4099425 B1EP 4099425B1EP-4099425-B1

Inventors

  • LEE, BYUNG YONG
  • LEE, UNG JU

Dates

Publication Date
20260513
Application Date
20211116

Claims (10)

  1. A method for evaluating insulation of an overlay part where an insulation coating layer has been laminated on a sliding portion of an electrode mixture layer, wherein the overlay part is a partial electrode portion where an insulation coating layer (13a) has been formed on an electrode mixture layer in an electrode including an insulation coating layer (12), and the sliding portion is the end of the electrode active material applied on the electrode current collector (11) at the time of electrode lamination, in which the thickness of the end gradually decreases, the method comprising: (a) a process of applying and drying insulation coating liquid (S) on the electrode mixture layer (12) to thereby simulate the overlay part, and collecting data about a length c of a gap of an applicator, a thickness d which has been increased by insulation coating, and a capacity f of the overlay part as measured by manufacturing a coin-half cell using a positive electrode including the simulated overlay part, and a counter electrode of lithium, and performing charge/discharge, and measuring discharge capacity f; (b) a process of applying and drying insulation coating liquid (S) on a current collector (11) to thereby simulate a pure insulation coating layer, and collecting data about a length g of a gap of an applicator and a thickness h of the pure insulation coating layer (13b); (c) a process of generating a relation formula 1 between thickness H of the pure insulation coating layer (13b) and capacity F of the overlay part based on data collected through the processes (a) and (b); (d) a process of measuring a thickness of a pure insulation coating layer (13b) at an electrode for evaluation; and (e) a process of calculating the capacity f of the overlay part by substituting the thickness of the pure insulation coating layer (13b) measured in the process (d) into the relation formula 1, wherein the process (c) comprises: (c-1) a process of deriving relation formula 2 between thickness D which has been increased by insulation coating and capacity F of the overlay part based on data about the capacity f of the overlay part according to the thickness d which has been increased by insulation coating, which has been collected during the process (a); (c-2) a process of deriving relation formula 3 between the thickness D which has been increased by insulation coating and the thickness H of the pure insulation coating layer (13b), based on data about the length c of the gap of the applicator and the thickness d which has been increased by insulation coating, collected during the process (a), and data about the length g of the gap of the applicator and the thickness h of the pure insulation coating layer (13b), collected during the process (b); and (c-3) a process of deriving the relation formula 1 by combination of the relation formula 2 and the relation formula 3, wherein the process (c-2) comprises: (c-2-1) a process of deriving relation formula 4 between length C of the gap of the applicator and thickness D which has been increased by insulation coating based on data about the length c of the gap of the applicator and the thickness d which has been increased by insulation coating, collected during the process (a); (c-2-2) a process of deriving relation formula 5 between length G of the gap of the applicator and thickness H of the pure insulation coating layer (13b), based on data about the length g of the gap of the applicator and the thickness h of the pure insulation coating layer (13b), collected during the process (b); and (c-2-3) a process of deriving relation formula 3 between thickness D which has been increased by insulation coating and thickness H of the pure insulation coating layer (13b) by eliminating a gap of the applicator, which is a parameter, by combination of the relation formula 4 and the relation formula 5.
  2. The method of claim 1, wherein the process (a) comprises: (a-1) a process of applying and drying insulation coating liquid (S) on the electrode mixture layer (12) to thereby simulate the overlay part, and measuring a length c of the gap of the applicator which applies the insulation coating liquid (S); (a-2) a process of measuring the thickness d which has been increased by insulation coating in the simulated overlay part; and (a-3) a process of measuring capacity f of the simulated overlay part, wherein data about the length c of the gap of the applicator, the thickness d which has been increased by insulation coating, and the capacity f of the overlay part is collected by repeating the processes (a-1) to (a-3).
  3. The method of claim 1, wherein the process (b) comprises: (b-1) a process of applying and drying insulation coating liquid (S) on the current collector (11) to thereby simulate the pure insulation coating layer (13b), and measuring a length g of the gap of the applicator which applies the insulation coating liquid (S); and (b-2) a process of measuring thickness h of the pure insulation coating layer (13b) simulated by the process (b-1), wherein data about the length g of the gap of the applicator which applies the insulation coating liquid (S), and the thickness h of the pure insulation coating layer (13b) is collected by repeating the processes (b-1) to (b-2).
  4. The method of claim 2, wherein the process (a-3) includes a process of manufacturing a coin cell including the simulated overlay part, and measuring capacity f of the overlay part by measuring a charge capacity or a discharge capacity of the coin cell.
  5. The method of claim 4, wherein the coin cell is a half cell.
  6. The method of claim 1, wherein part of the insulation coating liquid (S) applied on the electrode mixture layer (12) is permeated into the electrode mixture layer (12) during the simulating of the overlay part of the process (a).
  7. The method of claim 1, wherein the thickness d which has been increased by insulation coating is obtained by subtracting a thickness of the electrode mixture layer (12) before application of the insulation coating liquid (S) from a total thickness of the electrode mixture layer (12) and the insulation coating layer (13) after drying the insulation coating liquid (S).
  8. The method of claim 1, wherein the insulation coating layer (13) includes polyvinylidene fluoride (PVDF).
  9. The method of claim 1, wherein the electrode is a positive electrode.
  10. The method of claim 1, wherein the thickness of the pure insulation coating layer (13b) is equal to or less than 15 µ m.

Description

[Technical Field] The present invention relates to a method of evaluating insulation of an insulation coating layer, and specifically to a method of evaluating insulation of an overlay part without measuring the thickness of an insulation coating layer in an overlay part where the insulation coating layer has been laminated on an electrode mixture layer. [Background Art] As technology development and demand for mobile devices increase, the demand for batteries as an energy source is rapidly increasing, and among such secondary batteries, many studies have been conducted on lithium secondary batteries having a high energy density and a discharge voltage, and have been commercialized and widely used. When such a lithium secondary battery is exposed to a high temperature, there is a possibility that a short circuit occurs due to a contact between the positive electrode and the negative electrode. Further, even when a large electric current flows within a short period of time by overcharge, an external short circuit, nail penetration, a local crush, etc., there is a danger of ignition/explosion as the battery is heated by heat generation. Such a phenomenon usually occurs at the end of the electrode active material applied on the electrode current collector at the time of electrode lamination, and various methods to reduce the possibility of a short circuit of an electrode at an external shock or high temperature have been tried. FIG. 1 shows a process of applying insulation coating liquid on the end of a positive electrode mixture coated portion in order to prevent a short circuit of a positive electrode and a negative electrode. Referring to FIG. 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 insulation coating liquid is applied on the non-coated part around the end of the electrode mixture layer 12 and is dried to thereby form insulation coating layers 13a and 13b. Since the electrode mixture layer before being dried has fluidity, a sliding phenomenon, in which the thickness of the end gradually decreases, is shown. Further, since the insulation coating liquid is fluid, the insulation coating liquid is coated not only on the non-coated part, but also on the sliding portion of the electrode mixture layer. Hence, the finally formed insulation coating layer includes a pure insulation coating layer 13b formed on the non-coated part and an overlay part insulation coating layer 13a formed on the electrode mixture layer. In the electrode as shown in FIG. 1, the pure insulation coating layer blocks movement of electrons to thereby prevent a short circuit of the positive electrode and the negative electrode, and the overlay part insulation coating layer limits the movement of lithium ions to a non-existing place to thereby further improve safety of the battery. Further, since the insulation of the insulation coating layer is proportional to the thickness of the insulation coating layer, the insulating performance is managed by measuring the thickness of the insulation coating layer. In an electrode having an overlay part, the thickness of the coated pure insulation coating layer 13b can be easily measured, but in order to separately measure the thickness of the insulation coating layer 13a of the overlay part, new equipment should be introduced, which may take a lot of time and costs. Further, in the insulation coating layer of the overlay part, part of the insulation coating liquid is permeated into pores of the electrode mixture layer unlike the pure insulation coating layer, and accordingly, the insulating performance of the overlay part is shown by the action of both the insulating material of the insulation coating layer and the insulating material permeated into the electrode mixture layer. Hence, it is difficult to evaluate insulation by measuring the thickness of the insulation coating layer of the overlay part. As such, there is a need for a technology for predicting insulation of an overlay part using conventional management factors without introducing new equipment. KR 2016 0091732 A provides a method for preparing an anode where an anode material containing an anode active material is covered on one surface or both surfaces of a current collector, comprising the steps of: (a) covering the anode material containing the anode active material on one surface or both surfaces of the current collector; (b) preparing an insulation coating agent containing an ultraviolet (UV) ray curable material; (c) covering the insulation coating agent on a boundary portion between an anode material coated part and an anode uncoated part; and (d) irradiating the insulation agent with UV rays to cure the insulation agent for forming an insulation coating part. [Disclosure] [Technical Problem] The present invention is believed to solve at least some of the above problems. For example, an aspect of the present invention prov