Battery Separator Porous Layer Balancing Ion Flow and Peel Strength

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Solution Overview

Problem

Nonaqueous electrolyte secondary battery separators face challenges in achieving both favorable ion permeability and peeling strength as the thickness of the porous layer decreases, making it difficult to maintain performance.

Innovation Solution

A nonaqueous electrolyte secondary battery porous layer with a thickness of less than 8.0 μm, surface roughness of not more than 0.15 μm, and a filler composition where particles larger than 1.0 μm comprise no more than 5% of the total, combined with a resin content of 40-80 weight%, is used to enhance ion permeability and peeling strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the thickness of the porous layer is decreased to increase energy density, then the energy density is improved, but the ion permeability and peeling strength deteriorate

Engineering Contradiction:

Improveenergy densityVSAvoidion permeability and peeling strength

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The invention changes the surface roughness parameter (Ra ≤ 0.15 μm) and particle size distribution parameter (≤5% particles ≥1.0 μm) of the porous layer to achieve both thin thickness (<8.0 μm) and high performance. By controlling these parameters, the invention resolves the contradiction between reduced thickness for energy density and maintained ion permeability/peeling strength for reliability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite porous layer containing both resin and inorganic particles with specific size distribution. This composite structure provides both the mechanical strength needed for peeling resistance and the controlled porosity needed for ion permeability, even at thicknesses below 8.0 μm.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If the thickness of the porous layer is decreased to improve energy density, then the energy density is improved, but the manufacturing precision required increases

Engineering Contradiction:

Improveenergy densityVSAvoidsurface roughness and particle size control

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The invention specifies precise parameter ranges (Ra ≤ 0.15 μm, ≤5% particles ≥1.0 μm, thickness <8.0 μm) that, while stringent, provide clear manufacturing targets. These parameter specifications enable consistent production of thin separators with reliable performance through controlled synthesis processes.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12191439B2Nonaqueous electrolyte secondary battery porous layer

Publication Date: 2025.01.07 SSLM

AI summary

An aspect of the present invention provides a nonaqueous electrolyte secondary battery porous layer that has both favorable ion permeability and favorable peeling strength. A nonaqueous electrolyte secondary battery porous layer in accordance with an aspect of the present invention includes: a resin; and a filler, the nonaqueous electrolyte secondary battery porous layer having a thickness of less than 8.0 μm, the nonaqueous electrolyte secondary battery porous layer having a surface roughness (Ra) of not more than 0.15 μm.