Composite Separator for Lithium Battery Thermal Stability

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Solution Overview

Problem

Conventional lithium secondary battery separators lack high heat resistance, mechanical strength, and stability, leading to safety issues due to heat shrinkage and internal short circuits, particularly when used in high-temperature applications.

Innovation Solution

A high heat resistance composite separator is developed, featuring a porous substrate with an inorganic coating layer and a high heat resistance polymer coating layer, which includes inorganic particles and a binder polymer to enhance mechanical strength and thermal stability, while preventing heat shrinkage and maintaining adhesion with electrodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a polyolefin-based separator is used to achieve shut-down function, then ion permeability is improved, but heat resistance deteriorates causing shape loss at high temperature

Engineering Contradiction:

Improveshut-down functionVSAvoidheat resistance

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent applies composite materials by combining polyolefin base material with ceramic particles and polymer coatings to create a separator that maintains the shut-down function of polyolefin while adding high-temperature stability through ceramic components that do not melt at separator operating temperatures

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the physical and chemical parameters of the separator by incorporating ceramic particles with specific size distributions (0.1-10 μm) and using polymer coatings with specific thicknesses (1-10 μm) to achieve both shut-down capability and enhanced heat resistance without sacrificing ion permeability

Inventive Principle:

Principle #35Parameter changes

2Strength

If inorganic coating is applied to enhance mechanical strength, then strength is improved, but weight increases reducing energy density

Engineering Contradiction:

Improvemechanical strengthVSAvoidbattery weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent uses porous ceramic particles and maintains a porous structure in the coating layers to provide mechanical strength while minimizing weight addition. The porous structure allows ion transport and reduces the amount of material needed compared to dense coatings

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent applies coating layers selectively on specific surfaces of the separator rather than uniformly throughout, and uses different ceramic particle sizes in different regions to optimize strength where needed while minimizing overall weight increase

Inventive Principle:

Principle #3Local quality

3Area of stationary object

If separator area is increased to prevent electrode contact, then separation function is improved, but internal short circuit prevention deteriorates due to heat shrinkage

Engineering Contradiction:

Improveseparator areaVSAvoidshort circuit prevention

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent incorporates ceramic particles and polymer coatings with thermal expansion characteristics that counteract the shrinkage tendency of polyolefin at high temperatures, maintaining separator area and preventing electrode contact even when the base material attempts to shrink

Inventive Principle:

Principle #37Thermal expansion

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 composite separator provides superior safety and stability, suppressing heat shrinkage, maintaining ion conductivity, and improving the performance and life cycle of lithium secondary batteries without compromising electrochemical properties.

Implementation Method 1

an inorganic coating layer formed on one surface of the porous substrate, the inorganic coating layer including a plurality of inorganic particles and a binder polymer disposed on a portion or all of surfaces of the inorganic particles

Methodology Applied

Scientific EffectCoating: Coatings

Implementation Method 2

a high heat resistance polymer coating layer formed on the other surface of the porous substrate, the high heat resistance polymer coating layer including a high heat resistance polymer and inorganic particles dispersed in the high heat resistance polymer

Methodology Applied

Scientific EffectThermal resistance: Thermal Insulation

Implementation Method 3

a porous substrate having a plurality of pores

Methodology Applied

Scientific EffectIon permeability: Permeation

Data Source

PatentUS10090501B2High heat resistance composite separator for lithium secondary battery and lithium secondary battery including same

Publication Date: 2018.10.02 SEBANG LITHIUM BATTERY CO LTD

AI summary

Disclosed is a high heat resistance composite separator including a porous substrate having a plurality of pores, an inorganic coating layer formed on one surface of the porous substrate, the inorganic coating layer including a plurality of inorganic particles and a binder polymer disposed on a portion or all of surfaces of the inorganic particles to connect and bind the inorganic particles, and a high heat resistance polymer coating layer formed on the other surface of the porous substrate, the high heat resistance polymer coating layer including a high heat resistance polymer and inorganic particles dispersed in the high heat resistance polymer.