US-12625062-B2 - Method for evaluating adhesion of separator

US12625062B2US 12625062 B2US12625062 B2US 12625062B2US-12625062-B2

Abstract

A method for evaluating an adhesive strength of a separator including manufacturing an electrode-separator composite including an electrode stacked on at least one surface of a separator, and the at least one surface of the separator and a surface of the electrode facing the at least one surface include adhesive surfaces and non-adhesive surfaces, and the adhesive surfaces and the non-adhesive surfaces are alternately disposed; moving the electrode-separator composite; cutting the electrode-separator composite in a direction parallel to the moving direction; attaching measuring rolls respectively to both surfaces of the cut electrode-separator composite; separating the electrode-separator composite by rotating each of the attached measuring rolls and spacing the measuring rolls apart from each other; and measuring a torque generated by the measuring rolls while separating the electrode-separator composite.

Inventors

Hyun Kyung Shin
Jae Woong Yoo

Assignees

LG ENERGY SOLUTION, LTD.

Dates

Publication Date: 20260512
Application Date: 20221101
Priority Date: 20211119

Claims (20)

1 . A method for evaluating an adhesive strength of a separator that is configured to be disposed between a negative electrode of a battery and a positive electrode of the battery, the method comprising: manufacturing an electrode-separator composite including an electrode stacked on at least one surface of a separator, the at least one surface of the separator and a surface of the electrode facing the at least one surface including adhesive portions and non-adhesive portions, and the adhesive portions and the non-adhesive portions are alternately disposed; moving the electrode-separator composite; cutting the electrode-separator composite in a direction parallel to the moving direction; attaching measuring rolls respectively to both surfaces of the cut electrode-separator composite; separating the electrode-separator composite by rotating each of the attached measuring rolls and spacing the measuring rolls apart from each other; and measuring a torque generated by the measuring rolls while separating the electrode-separator composite.
2 . The method of claim 1 , wherein the manufacturing of the electrode-separator composite comprises: manufacturing a laminate by stacking the electrode on the at least one surface of the separator; and heating and pressurizing only a partial region of the laminate, wherein the partial region corresponds a region including the adhesive portions.
3 . The method of claim 2 , wherein the heating and pressurizing of only the partial region of the laminate includes heating and pressurizing the partial region at a temperature of 70° C. to 110° C. and a pressure of 20 kgf/cm 2 to 80 kgf/cm 2 .
4 . The method of claim 2 , wherein the manufacturing of the laminate and the heating and pressurizing of only the partial region of the laminate are performed simultaneously utilizing lamination rolls including a spaced pattern.
5 . The method of claim 4 , wherein the lamination rolls have grooves on circumferential surfaces of the lamination rolls.
6 . The method of claim 2 , wherein the heating and pressurizing of only the partial region of the laminate includes heating and pressurizing the partial region at a temperature of 60° C. to 120° C. and a pressure of 10 kgf/cm 2 to 100 kgf/cm 2 .
7 . The method of claim 1 , wherein at least one of the adhesive portions forms a stripe shape in a direction parallel to a rotating axis of a measuring roll among the measuring rolls.
8 . The method of claim 1 , wherein the measuring of the torque utilizes a torque sensor.
9 . The method of claim 1 , wherein the measuring of the torque comprises: measuring a first torque generated by the measuring rolls in response to the non-adhesive portions being separated by the measuring rolls; determining the measured first torque as a reference for zero-point adjustment; and measuring a second torque generated by the measuring rolls in response to the adhesive portions being separated by the measuring rolls.
10 . The method of claim 1 , further comprising: obtaining an adhesive strength from the measured torque, wherein the adhesive strength is calculated by Equation 1 below: S=F/d ×sin A [Equation 1] in the Equation 1: S is an adhesive strength (unit: kgf) of the separator, F is a magnitude (unit: kgf·m) of the measured torque generated by the measuring rolls while separating the electrode-separator composite, D is a shortest distance (unit: m) between the electrode and a rotating axis of at least one of the measuring rolls, and A is an angle (unit: rad) formed by the electrode-separator composite and the electrode after the separation.
11 . The method of claim 10 , wherein the manufacturing of the electrode-separator composite comprises: manufacturing a laminate by stacking the electrode on the at least one surface of the separator; and heating and pressurizing only a partial region of the laminate, wherein the partial region corresponds a region including the adhesive portions.
12 . The method of claim 11 , wherein the manufacturing of the laminate and the heating and pressurizing of only the partial region of the laminate are performed simultaneously utilizing lamination rolls including a spaced pattern.
13 . The method of claim 11 , wherein the heating and pressurizing of only the partial region of the laminate includes heating and pressurizing the partial region at a temperature of 60° C. to 120° C. and a pressure of 10 kgf/cm 2 to 100 kgf/cm 2 .
14 . The method of claim 10 , wherein at least one of the adhesive portions forms a stripe shape in a direction parallel to a rotating axis of a measuring roll among the measuring rolls.
15 . The method of claim 10 , wherein the measuring of the torque utilizes a torque sensor.
16 . The method of claim 10 , wherein the measuring of the torque comprises: measuring a first torque generated by the measuring rolls in response to the non-adhesive portions being separated by the measuring rolls; determining the measured first torque as a reference for zero-point adjustment; and measuring a second torque generated by the measuring rolls in response to the adhesive portions being separated by the measuring rolls.
17 . The method of claim 10 , wherein the obtaining of the adhesive strength from the measured torque includes evaluating the adhesive strength of the electrode-separator composite from a difference between a first adhesive strength calculated by the Equation 1 in response to the non-adhesive portions being separated by the measuring rolls and a second adhesive strength calculated by the Equation 1 in response to the adhesive portions being separated by the measuring rolls.
18 . The method of claim 1 , wherein a distance between the adhesive portions are the same.
19 . The method of claim 1 , wherein a distance between the adhesive portions are different.
20 . The method of claim 1 , wherein the measuring rolls include one or more pairs of measuring rolls, the one or more pairs of measuring rolls include a first measuring roll and a second measuring roll, the first measuring roll is attached to a first surface among the both surfaces of the cut electrode-separator composite, and the second measuring roll is attached to a second surface among the both surfaces of the cut electrode-separator composite.

Description

TECHNICAL FIELD This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0160462 filed with the Korean Intellectual Property Office on Nov. 19, 2021, the entire contents of which are incorporated herein by reference. The present application relates to a method for evaluating an adhesive strength of a separator. BACKGROUND ART The demand for secondary batteries such as electric vehicles and mobile devices is rapidly expanding, and there is an increasing need for the condition diagnosis and the quality stability of the secondary batteries. The secondary batteries may be divided into a nickel-cadmium battery, a nickel-metal hydride battery, a nickel-hydrogen battery, and a lithium secondary battery. Among the above-described secondary batteries, the lithium secondary battery has a higher operating voltage than the nickel-cadmium battery or nickel-metal hydride battery, and have an excellent characteristics of energy density per unit weight, such that they are mainly used in portable electronic devices or high-output hybrid vehicles. In general, the lithium secondary battery may include an electrode assembly having a positive electrode, a negative electrode, and a separator, electrode tabs extending from the electrode assembly, and electrode leads welded to the electrode tabs. In this case, the electrode assembly is a power generating element in which positive and negative electrodes are stacked with the separator interposed therebetween. In general, the electrode assembly is manufactured using a method in which the negative electrode, separator, and positive electrode are respectively manufactured in a separate process, and then laminated and adhered by applying heat and pressure at the same time. However, in the case of a high-capacity battery, the separator containing a less binder, that is, the thin separator with a low binder content, is often applied. For this reason, when the battery is manufactured in the above-mentioned method, there is a problem in that a sufficient adhesive strength is not secured between the electrode and the separator. Therefore, it is important to use the separator with an excellent adhesive strength to secure a sufficient adhesive strength. To this end, it is important to evaluate the adhesive strength of the separator. In the related art, as illustrated in FIG. 2, in order to evaluate the adhesive strength of the separator, a method for evaluating the adhesive strength in which a specimen of the separator and electrode manufactured by applying heat and pressure is prepared and a peel test is performed on the manufactured specimen is generally used. Specifically, the peel test is performed as illustrated in FIG. 2. A separator 1 with a width of 25 mm and a length of 60 mm and an electrode 2 are stacked, placed between a polyethylene terephthalate (PET) film 3, and pressed with a heated press. Thereby, an electrode-separator composite in which an adhesive strength is generated between the separator and the electrode is manufactured (FIG. 2A). A slide glass 6 is attached using a double-sided adhesive tape 5 to an electrode surface of the electrode-separator composite manufactured as described above, and the PET film is attached using a single-sided adhesive tape 4 to a partial region of a separator surface of the electrode-separator composite, resulting in manufacturing the specimen (FIG. 2B). The specimen manufactured as described above is mounted on a universal material testing machine and a force required to separate the separator and the electrode is measured (FIG. 2C). In this case, since the adhesive strength of the separator greatly fluctuates depending on a position, it is necessary to evaluate the adhesive strength by attaching the PET film to various positions on the separator surface of the electrode-separator composite. However, it takes a large amount of time to make several specimens and measure each one. Because of the above-mentioned restriction, there is a problem in that the evaluation (sampling inspection) of the adhesive strength of the separator is not sufficiently achieved. Therefore, there is a need for a new method for evaluating an adhesive strength of a separator which is capable of overcoming the above-described problem. DOCUMENT OF RELATED ART Korean Patent Publication No. 10-2016-0023072 DETAILED DESCRIPTION OF THE INVENTION Technical Problem The present application has been made in an effort to provide a method capable of efficiently performing an evaluation of an adhesive strength of a separator over a large region. Technical Solution An exemplary embodiment of the present disclosure provides a method for evaluating an adhesive strength of a separator, the method including: manufacturing an electrode-separator composite in which an electrode is stacked on at least one surface of a separator, and surfaces of the separator and the electrode facing each other include adhesive surfaces and non-adhesive surfaces of the s