Copolymer Electrolyte Ionic Conductivity Mechanical Strength

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Solution Overview

Problem

Polyethylene oxide-based polymer electrolytes for lithium secondary batteries face challenges in achieving high ionic conductivity while maintaining mechanical strength and stability, as enhancing ionic conductivity often compromises mechanical properties and vice versa.

Innovation Solution

A polymer electrolyte composition is developed by copolymerizing polyethylene glycol methacrylate (PEGMA) with methacrylic acid monomers containing an alkenyl group, followed by crosslinking with a photo-crosslinker and dispersing an alkali metal salt, to create a solid phase electrolyte with improved ionic conductivity and mechanical strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the liquidity of the polymer chains is increased to enhance ionic conductivity, then ionic conductivity is improved, but mechanical strength and physical properties are lowered

Engineering Contradiction:

Improveionic conductivityVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The polymer structure is segmented into distinct functional regions: hydrophilic segments containing polyethylene oxide chains for ion conduction, and hydrophobic segments providing mechanical strength. This segmentation allows each region to perform its specialized function without compromising the other, resolving the contradiction between ionic conductivity and mechanical strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention creates a composite polymer structure combining polar hydrophilic groups (for ionic conductivity) and non-polar hydrophobic groups (for mechanical strength) within a single polymer matrix. This composite approach enables simultaneous achievement of high ionic conductivity and adequate mechanical properties by leveraging the complementary characteristics of different chemical groups.

Inventive Principle:

Principle #40Composite materials

2Strength

If the mechanical strength of the polymer is elevated to improve physical properties, then mechanical strength is improved, but ionic conductivity is lowered

Engineering Contradiction:

Improvemechanical strengthVSAvoidionic conductivity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

Different regions of the polymer are assigned different local qualities: hydrophobic regions with high mechanical strength and hydrophilic regions with high ionic conductivity. The polymer contains both polar groups (for ion transport) and non-polar groups (for mechanical integrity) in specific proportions, allowing local optimization of properties without compromising overall performance.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If linear polyethylene oxide is used as solid electrolyte, then solid phase structure is achieved, but crystallizing area is broad and ionic conductivity is low

Engineering Contradiction:

Improvesolid phase structureVSAvoidionic conductivity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The invention changes the chemical parameters of the polymer by introducing functional groups with different polarities. By incorporating both polar (hydrophilic) and non-polar (hydrophobic) groups into the polymer chain, the crystallinity is reduced while maintaining solid phase structure, thereby enhancing ionic conductivity without sacrificing structural stability.

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

The approach results in a solid phase electrolyte with balanced ionic conductivity and mechanical strength, suitable for secondary battery applications, as demonstrated by the synthesis of copolymers like PHP, which exhibit high ionic conductivity and dimensional stability.

Implementation Method 1

crosslinking with a photo-crosslinker

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

alkali metal salts in the polymer may exist as stable ions since cations dissociated from the salts form a coordination complex

Methodology Applied

Scientific EffectIonic dissociation: Ionisation

Implementation Method 3

copolymerizing the monomers by mixing the PEGMA monomers and the ACMA monomers in organic solvent and adding an initiator to the mixture

Methodology Applied

Scientific EffectCopolymerization: Chemical Bonding

Data Source

PatentUS9887433B2Copolymer electrolytes for secondary battery, method for preparing the same and use thereof

Publication Date: 2018.02.06 SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION

AI summary

The present invention provides copolymers of polyethylene oxide methacrylate and alkenyl group-containing methacrylate, method for preparing the same and use thereof. The copolymers may be used for preparing solid phase electrolytes having high ionic conductivity and enhanced physical properties.