Polyolefin Battery Separator Orientation for Impact Absorbency

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Solution Overview

Problem

Conventional nonaqueous electrolyte secondary battery separators lack sufficient impact absorbency while maintaining good ion permeability, tear resistance, and flexibility.

Innovation Solution

A nonaqueous electrolyte secondary battery separator featuring a polyolefin porous film with a low orientation degree of molecular chains, characterized by a full width at half maximum of a peak of the MD component of not less than 30 degrees and a maximum-to-minimum intensity ratio r of not more than 3.6, enhancing impact absorbency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the c-axis of polyethylene crystal has high orientation degree in the machine direction, then cuttability and shutdown temperature are improved, but impact absorbency deteriorates

Engineering Contradiction:

ImprovecuttabilityVSAvoidimpact absorbency

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The invention changes the orientation parameter of polyethylene molecular chains from high orientation (conventional) to low orientation (≤30 degrees), as measured by azimuthal profile analysis. This parameter change resolves the contradiction by achieving both good cuttability and excellent impact absorbency simultaneously, unlike conventional high-orientation separators that fail impact tests.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the c-axis of polyethylene crystal has high orientation degree in the machine direction, then shutdown temperature is improved, but impact absorbency deteriorates

Engineering Contradiction:

Improveshutdown temperatureVSAvoidimpact absorbency

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention maintains the shutdown temperature function by preserving the polyethylene shutdown mechanism while changing the molecular orientation parameter to low orientation (≤30 degrees). This allows the separator to achieve both reliable shutdown temperature performance and excellent impact absorbency, resolving the contradiction between reliability and strength.

Inventive Principle:

Principle #35Parameter changes

3Strength

If molecular chains of polyolefin have low orientation degree, then impact absorbency is improved, but ion permeability and tear resistance may deteriorate

Engineering Contradiction:

Improveimpact absorbencyVSAvoidion permeability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention optimizes the orientation parameter to a specific range (≤30 degrees) rather than complete random orientation, maintaining sufficient structural integrity for ion permeability and tear resistance while achieving excellent impact absorbency. This controlled parameter change resolves the contradiction between strength and reliability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates different local structural characteristics: low orientation in the plane direction for impact absorbency, while maintaining appropriate porosity and pore structure for ion permeability. This local quality differentiation allows simultaneous achievement of impact resistance and ion transport functionality.

Inventive Principle:

Principle #3Local quality

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

The separator achieves excellent impact absorbency while maintaining good ion permeability, tear resistance, and flexibility, effectively addressing the limitations of conventional separators.

Implementation Method 1

a separator including a porous film which contains polyolefin as a main component, wherein molecular chains of the polyolefin have a low orientation degree, has excellent impact absorbency

Methodology Applied

Scientific EffectImpact absorption: Absorption (physical)

Implementation Method 2

maintaining good ion permeability

Methodology Applied

Scientific EffectIon permeation: Permeation

Data Source

PatentUS12334590B2Nonaqueous electrolyte secondary battery separator, nonaqueous electrolyte secondary battery member, and nonaqueous electrolyte secondary battery

Publication Date: 2025.06.17 SSLM

AI summary

A nonaqueous electrolyte secondary battery separator having excellent impact absorbency includes a polyolefin porous film having a full width W at half maximum of a peak of an MD component of not less than 30 degrees. The full width W at half maximum of the peak of the MD component is calculated from an azimuthal profile of a scattering peak on a plane obtained by wide-angle X-ray scattering measurement that is carried out by irradiating a surface of the polyolefin porous film with an X-ray from a direction vertical to the surface of the polyolefin porous film, and/or having a maximum-to-minimum intensity ratio r of not more than 3.6. The maximum-to-minimum intensity ratio r is calculated from a Fourier transformed azimuthal profile obtained by observing the surface of the polyolefin porous film by SEM.