Separator Coating with Alumina and Aluminum Hydroxide for Thermal Stability

Solution Overview

Problem

Current lithium ion batteries face safety issues due to severe thermal contraction of polyolefin-based separators, leading to potential short circuits and explosions, especially at high temperatures, and existing solutions with large particle sizes face stability and processability challenges.

Innovation Solution

A separator with a porous organic-inorganic coating layer comprising alumina and aluminum hydroxide particles of varying sizes, where the aluminum hydroxide particles have a smaller average particle size than alumina, is used to minimize thermal contraction and improve stability, with a binder polymer to connect and immobilize the inorganic particles, enhancing mechanical and electrical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If large particle size inorganic particles are used in the porous coating layer, then thermal contraction control is difficult, but manufacturing processability is improved

Engineering Contradiction:

Improvethermal contraction controlVSAvoidcoating layer stability and processability

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The patent applies local quality by using inorganic particles with different particle sizes at different locations or roles within the coating layer. Specifically, it uses a mixture of fine particles (0.1-10 μm) and coarse particles (10-50 μm) where the fine particles fill gaps and provide thermal stability while the coarse particles provide structural framework and manufacturing ease.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining inorganic particles of different sizes (fine and coarse) within the same coating layer. This composite structure allows the fine particles to control thermal contraction through their high surface area and thermal responsiveness, while the coarse particles maintain structural integrity and facilitate manufacturing processability.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If small particle size inorganic particles are used in the porous coating layer, then coating layer stability and processability improve, but thermal contraction control becomes difficult

Engineering Contradiction:

Improvecoating layer stability and processabilityVSAvoidthermal contraction control

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by using inorganic particles with different particle sizes at different locations or roles within the coating layer. Specifically, it uses a mixture of fine particles (0.1-10 μm) and coarse particles (10-50 μm) where the fine particles fill gaps and provide thermal stability while the coarse particles provide structural framework and manufacturing ease.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining inorganic particles of different sizes (fine and coarse) within the same coating layer. This composite structure allows the fine particles to control thermal contraction through their high surface area and thermal responsiveness, while the coarse particles maintain structural integrity and facilitate manufacturing processability.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If polyolefin-based porous substrate is used for separator, then manufacturing ease is improved, but thermal shrinkage increases causing safety problems

Engineering Contradiction:

Improveseparator manufacturingVSAvoidthermal shrinkage and safety

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent converts the harmful thermal shrinkage property of polyolefin substrates into a beneficial feature by applying a porous coating layer containing inorganic particles. The coating layer's thermal behavior compensates for and counteracts the substrate's shrinkage, transforming the safety hazard into an opportunity for enhanced thermal stability through the synergistic combination of organic substrate and inorganic coating.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent employs composite materials by combining the polyolefin porous substrate with a porous coating layer containing inorganic particles. This composite structure allows the polyolefin substrate to provide manufacturing ease and flexibility, while the inorganic coating layer provides thermal stability and shrinkage resistance, resolving the contradiction between ease of manufacture and safety.

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 proposed separator significantly reduces thermal shrinkage, preventing short circuits and internal overheating, while reducing the weight and improving heat absorption, thus enhancing the safety and performance of electrochemical devices.

Implementation Method 1

reducing the weight and improving heat absorption, thus enhancing the safety and performance of electrochemical devices

Methodology Applied

Scientific EffectHeat absorption: Absorption (physical)

Implementation Method 2

the porous coating layer comprising alumina and aluminum hydroxide particles of varying sizes

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

a binder polymer to connect and immobilize the inorganic particles

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS10586969B2Separator and electrochemical device comprising same

Publication Date: 2020.03.10 LG ENERGY SOLUTION LTD

AI summary

Disclosed are a separator and an electrochemical device comprising the same, the separator comprising: a porous substrate having a plurality of pores; and a porous coating layer formed on at least one surface of the porous substrate or at least one surface of the porous substrate and a portion of the pore, the porous coating layer containing a plurality of inorganic particles and a binder polymer disposed on a part or the entirety of a surface of the inorganic particle to connect and fix the inorganic particles, wherein the inorganic particle comprises an alumina particle and an aluminum hydroxide particle having a smaller average particle diameter than the alumina particle.