Lithium Battery Separator Coating via Epoxy Bonding

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Solution Overview

Problem

Lithium secondary batteries face limitations in safety and capacity due to low adhesion between the gel polymer electrolyte and the separator, leading to increased interfacial resistance and vulnerability to thermal runaway.

Innovation Solution

A lithium secondary battery design featuring a separator with a coating layer containing an organic binder and inorganic particles, where the organic binder and gel polymer electrolyte are bonded through an epoxy ring-opening reaction, enhancing adhesion and mechanical stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a gel polymer electrolyte is used to improve safety, then safety is improved, but adhesion to the separator deteriorates

Engineering Contradiction:

ImprovesafetyVSAvoidadhesion

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent uses a composite coating layer comprising inorganic particles (such as Al2O3, SiO2, TiO2, or ZnO) dispersed in a polymer matrix (polyvinylidene fluoride or polyacrylonitrile) on the separator surface. This composite structure provides both mechanical strength and chemical functionality for epoxy bonding, resolving the contradiction between safety improvement through gel polymer electrolyte and adhesion to the separator.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent introduces epoxy functional groups into the coating layer to enable chemical bonding with the gel polymer electrolyte. By changing the chemical parameters of the coating layer (adding epoxy groups through specific polymer selection or surface treatment), the adhesion is significantly improved while maintaining the safety benefits of the gel polymer electrolyte.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the separator uses polyethylene to provide shutdown function, then safety function is improved, but high-temperature stability deteriorates

Engineering Contradiction:

Improveshutdown functionVSAvoidhigh-temperature stability

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent creates a composite coating layer on the polyethylene separator that combines the shutdown function of PE with the high-temperature stability of inorganic particles and thermally stable polymers. The coating layer acts as a protective barrier that maintains separator functionality at elevated temperatures while preserving the shutdown mechanism at lower temperatures.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies different functional layers to different aspects of separator performance: the polyethylene base layer provides shutdown function at low temperatures, while the inorganic-polymer coating layer provides high-temperature stability. This local differentiation of material properties resolves the contradiction between shutdown function and high-temperature stability.

Inventive Principle:

Principle #3Local quality

3Duration of action of stationary object

If a coating layer with inorganic particles and polymer binder is applied to enhance durability, then durability is improved, but adhesion to gel polymer electrolyte deteriorates

Engineering Contradiction:

ImprovedurabilityVSAvoidadhesion

Core Design Contradiction:

Duration of action of stationary objectVSUse of energy by moving object

Solution Approach 1:

The patent uses a composite coating layer with specific polymer matrices (polyvinylidene fluoride or polyacrylonitrile) containing inorganic particles, where the polymer is selected or modified to contain epoxy functional groups. This composite structure provides both durability through inorganic reinforcement and adhesion through epoxy bonding capability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the chemical composition parameters of the coating layer by introducing epoxy functional groups into the polymer binder or through surface treatment of inorganic particles. This parameter change enables chemical bonding with the gel polymer electrolyte while maintaining the durability benefits of the inorganic-polymer composite structure.

Inventive Principle:

Principle #35Parameter changes

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

Improved adhesion between the gel polymer electrolyte and the separator reduces interfacial resistance, enhances capacity characteristics, and increases mechanical and high-temperature safety, preventing short circuits and thermal runaway.

Implementation Method 1

the organic binder and the gel polymer electrolyte are bonded by an epoxy ring-opening reaction

Methodology Applied

Scientific EffectEpoxy ring-opening reaction: Chemical Bonding

Data Source

PatentUS11658301B2Lithium secondary battery and method of preparing the same

Publication Date: 2023.05.23 LG ENERGY SOLUTION LTD

AI summary

The present invention relates to a lithium secondary battery including a positive electrode, a negative electrode, a separator, which includes a coating layer including an organic binder and inorganic particles, and a gel polymer electrolyte formed by polymerization of an oligomer, wherein the organic binder and the gel polymer electrolyte are bonded by an epoxy ring-opening reaction, and a method of preparing the same.