Separator with Collapsing Porous Surface for Battery Electrode Expansion

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Solution Overview

Problem

Lithium ion secondary batteries with metal-based negative electrode active materials face issues due to significant volume expansion during charging, leading to tensile stress on current collectors and potential breakage, as well as shearing stress on electrode collectors, which can result in damage or breakage of both positive and negative electrodes.

Innovation Solution

A separator with a porous film base material and a porous surface layer containing inorganic particles and a resin material, featuring a rugged surface shape with an arithmetic mean surface roughness of 1.0 to 4.0 μm, which absorbs the expansion of the negative electrode active material layer, thereby preventing damage to the electrodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If metal-based negative electrode active materials (silicon, tin) are used to increase capacity, then the theoretical capacity is improved, but the volume expansion during charging causes tensile stress on current collectors leading to breakage

Engineering Contradiction:

Improvetheoretical capacityVSAvoidcurrent collector strength

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The patent applies porous materials by forming a porous coating layer on the current collector surface. This porous structure accommodates the volume expansion of metal-based negative electrode active materials during charging, reducing tensile stress on the current collector and preventing breakage while maintaining high capacity

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent uses composite materials by creating a composite structure consisting of the current collector, porous coating layer, and metal-based negative electrode active material. This composite design allows the porous coating layer to buffer volume changes while the metal-based material provides high capacity

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If metal-based negative electrode active materials are used to increase capacity, then the theoretical capacity is improved, but shearing stress is exerted on electrode collectors causing damage or breakage

Engineering Contradiction:

Improvetheoretical capacityVSAvoidshearing stress

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The porous coating layer absorbs and distributes the shearing stress generated during volume expansion, preventing concentrated stress points that would cause damage or breakage to the electrode collectors while maintaining the high capacity benefits of metal-based materials

Inventive Principle:

Principle #31Porous materials

3Reliability

If the separator surface is made smooth to ensure good contact with electrodes, then electrical contact is improved, but the separator cannot absorb expansion of negative electrode active material layer

Engineering Contradiction:

Improveelectrical contactVSAvoidexpansion absorption

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The separator surface is made porous to provide both good electrical contact through the porous structure and expansion absorption capability. The porous features allow the separator to conform to electrode surface irregularities while accommodating volume changes during charging

Inventive Principle:

Principle #31Porous materials

4Adaptability or versatility

If the separator surface is made rough to absorb expansion, then expansion absorption is improved, but electrical contact with electrodes deteriorates

Engineering Contradiction:

Improveexpansion absorptionVSAvoidelectrical contact

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The porous structure provides controlled roughness that enables expansion absorption while maintaining electrical contact. The porosity allows the separator to deform and conform to electrode surfaces, ensuring good contact even with the rough texture needed for buffering volume changes

Inventive Principle:

Principle #31Porous materials

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 effectively prevents damage and breakage of electrodes by collapsing to absorb the expansion of the negative electrode active material layer, maintaining electrode integrity and enhancing the performance and safety of lithium ion secondary batteries.

Implementation Method 1

the separator effectively prevents damage and breakage of electrodes by collapsing to absorb the expansion of the negative electrode active material layer

Methodology Applied

Scientific EffectCollapse: Deformation

Data Source

PatentUS9065121B2Separator and nonaqueous electrolyte battery

Publication Date: 2015.06.23 MURATA MFG CO LTD

AI summary

A separator is provided. The separator includes a base layer and a surface layer, wherein the surface layer is on at least one side of the base layer, and wherein the surface layer is structured so as to collapse at time of charging to prevent damage to a negative electrode due to expansion thereof. A battery including the separator is also provided. An electric device, an electric vehicle, and an electrical storage device including the battery are further provided.