Block Copolymer Electrolyte for Lithium Battery Stability

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Solution Overview

Problem

Lithium secondary batteries face issues with ion conductivity at room temperature and mechanical properties, leading to potential short-circuits and dendrite formation due to the use of existing electrolytes like PEO and PEO-PS block copolymers.

Innovation Solution

A block copolymer electrolyte with a co-continuous domain containing an ion conductive phase and a structural phase, where the structural phase has a glass transition temperature equal to or lower than room temperature, is developed, incorporating a polymerization product of monofunctional, multifunctional, and reactive polymerizable monomers to enhance mechanical properties and ion conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If PEO electrolyte is used, then ion conductivity is excellent at high temperature, but ion conductivity deteriorates at room temperature

Engineering Contradiction:

Improveion conductivityVSAvoidoperating temperature range

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent uses a block copolymer electrolyte composed of PEO blocks (for ion conductivity) and PMMA blocks (for mechanical strength and low glass transition temperature). This composite structure combines the advantages of both polymer systems to achieve both high ion conductivity and low-temperature operation capability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies the glass transition temperature parameter of the electrolyte by incorporating PMMA segments with low Tg (around -30°C to 0°C) into the block copolymer structure. This parameter change enables the electrolyte to maintain flexibility and ion conductivity at room temperature while preserving high-temperature performance

Inventive Principle:

Principle #35Parameter changes

2Strength

If PEO-PS block copolymer electrolyte is used, then mechanical properties need improvement, but ion conductivity is maintained

Engineering Contradiction:

Improvemechanical propertiesVSAvoidion conductivity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent replaces the polystyrene (PS) block with poly(methyl methacrylate) (PMMA) block in the block copolymer structure. PMMA provides superior mechanical properties including higher tensile strength and elongation at break compared to PS, while maintaining the phase-separated morphology necessary for ion conductivity

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent creates a microphase-separated structure where PEO domains (with high ion conductivity) are dispersed within a PMMA matrix (with excellent mechanical properties). This local differentiation of material properties allows simultaneous optimization of both ion conductivity and mechanical strength in different regions of the electrolyte

Inventive Principle:

Principle #3Local quality

3Strength

If electrolyte with high mechanical strength is used, then cracks are prevented, but dendrite formation may occur due to poor ion conductivity

Engineering Contradiction:

Improvemechanical strengthVSAvoiddendrite formation

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The block copolymer electrolyte combines PEO's high lithium ion mobility (reducing dendrite risk) with PMMA's mechanical strength (preventing cracks). The synergistic composite structure addresses both harmful factors simultaneously

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent converts the potential harm of rigid structures (which may cause stress concentration and dendrites) into benefit by using semi-crystalline PEO domains within the PMMA matrix. The crystalline PEO regions provide structured ion transport pathways that guide lithium ion flow, preventing dendrite formation while the amorphous PMMA matrix provides flexibility

Inventive Principle:

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

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 new electrolyte improves cycle efficiency and stability of lithium secondary batteries by maintaining excellent ion conductivity and mechanical strength, preventing cracks and dendrite formation, thus enhancing battery performance.

Implementation Method 1

performing polymerization of an electrolyte composition including: a chain transfer agent containing an ion conductive polymer, which is a polymer for forming an ion conductive phase; and the electrolyte composition including: i) a monofunctional polymerizable monomer, ii) a multifunctional polymerizable monomer, and iii) a polymerizable monomer having a reactive functional group, which are monomers for forming a structural phase polymer

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Data Source

PatentUS10361456B2Electrolyte, method of preparing the electrolyte, and secondary battery including the electrolyte

Publication Date: 2019.07.23 SAMSUNG ELECTRONICS CO LTD

AI summary

An electrolyte including a block copolymer containing a co-continuous domain including an ion conductive phase and a structural phase, wherein the structural phase includes a polymer segment having a glass transition temperature that is equal to or lower than room temperature.