Separator Sheet Cutting for Secondary Battery Gas Discharge

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Solution Overview

Problem

Secondary batteries face issues with gas traps forming on the electrode surface during charging and discharging, leading to inactive areas and lithium precipitation, which degrade capacity and increase cell resistance.

Innovation Solution

A secondary battery manufacturing apparatus and method that includes a folding device to stack electrodes, a cutting device to form continuous cutting regions on the separator sheet, and a taping device to attach tapes, creating gas passages through the separator sheet to facilitate quick gas discharge during the degassing process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the separator sheet is intact without cutting regions, then the electrode assembly maintains structural integrity, but gas traps form during charging and discharging leading to inactive areas and lithium precipitation

Engineering Contradiction:

Improvebattery reliabilityVSAvoidgas traps

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The separator sheet is divided into multiple regions by forming cutting regions that extend through its thickness. These cutting regions create separate compartments or segments within the electrode assembly, preventing gas accumulation and traps while maintaining overall structural integrity through the remaining intact separator portions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cutting regions create porous or open pathways through the separator sheet, allowing gas to escape during charging and discharging cycles. This porous structure prevents gas trap formation while the surrounding intact separator material maintains structural integrity and prevents electrode shorting.

Inventive Principle:

Principle #31Porous materials

2Object-generated harmful factors

If cutting regions are formed in the separator sheet to enable gas discharge, then gas traps are prevented, but the structural integrity of the separator sheet is compromised

Engineering Contradiction:

Improvegas trap preventionVSAvoidseparator sheet strength

Core Design Contradiction:

Object-generated harmful factorsVSStrength

Solution Approach 1:

The separator sheet is segmented into cutting regions and intact regions, where only specific portions are cut to allow gas discharge. The intact regions maintain structural strength and prevent electrode shorting, while the cutting regions provide gas escape pathways. This segmentation resolves the contradiction by localizing the structural compromise to non-critical areas.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the separator sheet have different properties: cutting regions are open or porous to allow gas passage, while surrounding regions remain intact to maintain structural integrity. This local differentiation of quality allows the separator to simultaneously provide gas discharge pathways and mechanical strength where needed.

Inventive Principle:

Principle #3Local quality

3Productivity

If continuous cutting regions extend through the entire separator sheet, then gas discharge efficiency is maximized, but the manufacturing complexity increases

Engineering Contradiction:

Improvegas discharge efficiencyVSAvoidcutting device complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The cutting regions are segmented into discrete portions rather than requiring complex continuous cutting patterns. This segmentation simplifies the cutting device design and operation while still achieving effective gas discharge through multiple distributed opening locations throughout the separator sheet.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of cutting the entire separator sheet uniformly, only specific partial regions are cut to the extent necessary for gas discharge. This partial action approach achieves sufficient gas discharge efficiency without requiring excessive cutting complexity, maintaining manufacturing simplicity while preventing gas traps.

Inventive Principle:

Principle #16Partial or excessive action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Prevents gas traps in the electrode assembly, enhancing the reliability of secondary batteries by ensuring efficient gas discharge and preventing capacity degradation and lithium precipitation.

Implementation Method 1

the cutting device includes a laser cutter configured to cut the separator sheet with a laser beam

Methodology Applied

Scientific EffectLaser: Laser

Data Source

PatentEP4712187A1Apparatus for manufacturing secondary battery and method for manufacturing secondary battery

Publication Date: 2026.03.18 LG ENERGY SOLUTION LTD

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Figure 2b
Figure 3a

AI summary

Disclosed herein relates to a secondary battery manufacturing apparatus including: a folding device configured to manufacture an electrode assembly, the electrode assembly comprising a plurality of unit cells stacked in a first direction and a separator sheet wound to cover an upper surface, a bottom surface, a first side, and a second side of each of the plurality of unit cells; a cutting device configured to cut a first side part of the separator sheet to form a first cutting region extending in a second direction on the separator sheet; and a taping device configured to attach a tape connecting two portions of the separator sheet separated by the first cutting region to the separator sheet.