Asymmetrical Pore Separator for Lithium-Ion Battery Dendrite Control

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Solution Overview

Problem

Current separators for high energy electrochemical cells face challenges such as mechanical instability, low thermal stability, and dendrite growth, leading to short circuiting and reduced battery life, especially in lithium-ion batteries.

Innovation Solution

A separator with a flexible perforate support and a porous ceramic material comprising multiple layers with varying pore sizes, where the second layer has a smaller average pore size than the first layer, providing enhanced ion conductivity and preventing dendrite growth, while maintaining mechanical stability and safety features like shutdown mechanisms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thin separator is used to minimize internal resistance and space requirements, then ion conductivity improves, but mechanical stability deteriorates leading to breakage and short circuiting

Engineering Contradiction:

Improveion conductivityVSAvoidmechanical stability

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The separator combines a polyolefin base material with a ceramic coating layer to create a composite structure. The polyolefin provides mechanical stability and shutdown safety, while the ceramic coating enhances thermal stability and prevents dendrite growth, allowing the separator to be thin without sacrificing mechanical strength.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The separator utilizes a porous ceramic coating layer with controlled pore structure that maintains high ion permeability while providing mechanical reinforcement. The porous structure allows efficient ion transport through the thin separator while the ceramic material provides the necessary mechanical strength to prevent breakage.

Inventive Principle:

Principle #31Porous materials

2Reliability

If high porosity is used to ensure low internal resistance, then ion conductivity improves, but mechanical strength deteriorates making the separator more prone to breaking

Engineering Contradiction:

Improveion conductivityVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The composite structure combines a mechanically strong polyolefin base material with a porous ceramic coating. The base material provides the necessary mechanical strength, while the porous ceramic coating provides ion conductivity pathways, allowing the separator to maintain both high porosity and mechanical strength simultaneously.

Inventive Principle:

Principle #40Composite materials

3Object-affected harmful factors

If organic polyolefin separators are used to achieve flexibility and shutdown safety, then safety improves, but thermal stability deteriorates at temperatures above 150°C

Engineering Contradiction:

Improveshutdown safetyVSAvoidthermal stability

Core Design Contradiction:

Object-affected harmful factorsVSTemperature

Solution Approach 1:

The separator combines a polyolefin base material that provides shutdown safety through melting at low temperatures with a ceramic coating layer that provides high-temperature thermal stability. The ceramic coating prevents thermal degradation and dendrite growth at temperatures above 150°C while the polyolefin base material maintains shutdown functionality.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different regions of the separator have different properties: the polyolefin base material provides shutdown safety at lower temperatures, while the ceramic coating layer provides thermal stability at high temperatures. This local differentiation of material properties allows the separator to address multiple thermal requirements simultaneously.

Inventive Principle:

Principle #3Local quality

4Temperature

If inorganic nonwoven or ceramic paper separators are used to improve thermal stability, then thermal stability improves, but mechanical stability deteriorates causing easy breakage

Engineering Contradiction:

Improvethermal stabilityVSAvoidmechanical stability

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The separator combines a mechanically flexible and strong polyolefin base material with a thin ceramic coating layer. The polyolefin base provides the necessary mechanical stability and flexibility to prevent breakage, while the ceramic coating provides thermal stability without requiring the separator to be thick or rigid.

Inventive Principle:

Principle #40Composite 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 solution achieves high ion conductivity, prevents dendrite formation, and ensures safety by maintaining mechanical stability and preventing short circuiting, even at low layer thicknesses, thus extending battery life and ensuring safe operation.

Implementation Method 1

a porous ceramic material which fills the perforations in the support and is suitable for receiving an ion-conducting electrolyte

Methodology Applied

Scientific EffectIon conductivity: Conduction (electrical)

Data Source

PatentUS7709140B2Separator provided with asymmetrical pore structures for an electrochemical cell

Publication Date: 2010.05.04 EVONIK OPERATIONS GMBH

AI summary

A separator for an electrochemical cell, comprising (A) a flexible perforate support, and (B) a porous ceramic material which fills the perforations in the support and is suitable for receiving an ion-conducting electrolyte, wherein the porous ceramic material comprises a first porous layer which is characterized by an average pore size and also at least one second porous layer for contacting with an electrode, the second porous layer having an average pore size which is smaller than the average pore size of the first porous layer.