Separator End-Part Removal for Uniform Coating

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Solution Overview

Problem

In the production of separators for lithium-ion secondary batteries, the separator original sheet tends to sag and flare at its end parts during the coating process, leading to non-uniform film thickness of the functional layer, and increasing the risk of the sheet breaking or forming wrinkles when high tension is applied to prevent sagging.

Innovation Solution

A method and device that involves removing the end parts of the base film in the width direction before coating, followed by a second removal of end parts after coating, to ensure a uniform film thickness and prevent sagging and wrinkling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If high tension is applied to the separator original sheet to prevent sagging, then the sheet flatness is improved, but the sheet may break or form wrinkles

Engineering Contradiction:

Improvesheet flatnessVSAvoidsheet integrity

Core Design Contradiction:

ShapeVSReliability

Solution Approach 1:

The patent removes the problematic end parts of the separator original sheet that are prone to sagging and flaring. By extracting these unstable regions before coating, the remaining central portion maintains flatness without requiring high tension, thus preventing sheet breakage and wrinkle formation while achieving the desired flatness for uniform coating.

Inventive Principle:

Principle #2Taking out (Extraction)

2Manufacturing precision

If the separator original sheet is transferred at high tension to maintain flatness, then coating uniformity is improved, but the sheet may stretch and deform

Engineering Contradiction:

Improvecoating uniformityVSAvoidsheet deformation

Core Design Contradiction:

Manufacturing precisionVSShape

Solution Approach 1:

The patent performs a preliminary removal of the end parts of the separator original sheet before the coating process. This preliminary action eliminates the unstable regions that would require high tension during transfer, allowing the sheet to be handled at lower tensions while still achieving uniform coating on the remaining stable portion.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If the end parts of the separator original sheet are removed, then coating uniformity is improved, but material waste increases

Engineering Contradiction:

Improvefilm thickness uniformityVSAvoidbase film waste

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent converts the harmful effect of end-part sagging and flaring (which causes coating defects) into a beneficial outcome by deliberately removing these end parts. Although this results in some material waste, it eliminates the need for high tension handling that would cause even greater waste through sheet breakage and wrinkle formation, ultimately improving overall manufacturing efficiency and product quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS9859539B2Method for producing separator and device for producing separator

Publication Date: 2018.01.02 SUMITOMO CHEM CO LTD

AI summary

A method for producing a separator in accordance with an embodiment of the present invention includes: a removing step of removing both end parts of a separator original sheet in a width direction of the separator original sheet, the separator original sheet being transferred; and a coating step of coating, with coating for forming a heat-resistant layer, the separator original sheet whose both end parts have been removed in the removing step.