Gel Polymer Electrolyte Composition for Lithium Battery Safety

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Solution Overview

Problem

Lithium secondary batteries face safety issues due to the low high-temperature safety of liquid electrolytes, which can lead to combustion and thermal runaway when exposed to high temperatures and high voltages, necessitating the development of a gel polymer electrolyte with improved safety features.

Innovation Solution

A composition for a gel polymer electrolyte is developed, comprising an oligomer with specific structural units, an additive such as a phosphate-based or benzene-based compound, a polymerization initiator, a lithium salt, and a non-aqueous solvent, forming a polymer network that enhances electrochemical safety and stability, thereby controlling heat generation and suppressing exothermic reactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a liquid electrolyte consisting only of an organic solvent and a salt is used, then the battery can operate with good ionic conductivity, but the high-temperature safety deteriorates due to low flash point and spontaneous combustion risk

Engineering Contradiction:

Improvehigh-temperature safetyVSAvoidcombustion risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent uses a composite gel polymer electrolyte system combining polyacrylonitrile polymer matrix with cyclic carbonate and chain carbonate solvents. This composite structure provides both the ionic conductivity of liquid electrolytes and the high-temperature safety of gel polymers, resolving the contradiction between conductivity and safety.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the physical state of the electrolyte from liquid to gel by controlling the polymer concentration (10-40 wt%), solvent ratio (cyclic to chain carbonate), and crosslinking degree. These parameter changes transform the electrolyte properties to achieve both good conductivity and high-temperature stability.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If a gel polymer electrolyte is used to improve high-temperature safety, then the flash point increases and thermal stability improves, but the ionic conductivity and battery performance may deteriorate

Engineering Contradiction:

Improvethermal stabilityVSAvoidionic conductivity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent creates local mobile phases within the gel polymer matrix by using cyclic carbonate solvents that can move freely in the polymer network. This local quality differentiation allows the gel structure to provide thermal stability while the mobile solvent regions maintain ionic conductivity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The cyclic carbonate solvent acts as an intermediary between the polymer matrix and lithium salt, facilitating ion transport through the gel structure. It mediates between the rigid polymer framework and the need for ion mobility, maintaining conductivity while preserving thermal stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If the polymer concentration in the gel electrolyte is increased to improve mechanical strength and safety, then the thermal stability improves, but the viscosity increases and ion transport becomes more difficult

Engineering Contradiction:

Improvemechanical strengthVSAvoidion transport resistance

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The patent segments the gel structure into polymer network regions (for mechanical strength) and solvent-rich channels (for ion transport). This segmentation allows the system to simultaneously achieve high mechanical strength and low ion transport resistance by separating the functions into different spatial regions.

Inventive Principle:

Principle #1Segmentation

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 gel polymer electrolyte composition significantly improves the high-temperature safety of lithium secondary batteries by reducing volatility and enhancing electrochemical stability, preventing ignition and thermal runaway, while maintaining battery performance.

Implementation Method 1

a polymerization initiator

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Implementation Method 2

controlling heat generation and suppressing exothermic reactions

Methodology Applied

Scientific EffectExothermic reaction suppression: Exothermic Reaction

Data Source

PatentUS11581577B2Composition for gel polymer electrolyte including fluoroalkylene oligomer, lithium salt, and phosphate or boran-based additive, gel polymer electrolyte prepared therefrom, and lithium secondary battery including the gel polymer electrolyte

Publication Date: 2023.02.14 LG ENERGY SOLUTION LTD

AI summary

The present invention provides a composition for a gel polymer electrolyte, the composition including: an oligomer represented by Formula 1; an additive; a polymerization initiator; a lithium salt; and a non-aqueous solvent, the additive including at least one compound selected from the group consisting of a substituted or unsubstituted phosphate-based compound and a substituted or unsubstituted benzene-based compound, a gel polymer electrolyte prepared using the same, and a lithium secondary battery.