Functionalized Ionic Liquid Electrolytes for Graphite Anode Stability

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Solution Overview

Problem

Lithium-ion batteries using conventional ionic liquids face issues with low lithium transference number, low ionic conductivity at low temperatures, and incompatibility with graphite anodes, leading to polarization and poor surface electrolyte interphase formation.

Innovation Solution

A non-flammable electrolyte formulation comprising functionalized ionic liquids, organic hybrid materials with nanoparticles, alkali metal salts, and organic co-solvents, which prevents cationic co-intercalation and promotes stable surface electrolyte interphase formation with graphite anodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional ionic liquids are used as electrolytes, then non-flammability and thermal stability are improved, but compatibility with graphite anodes deteriorates due to cationic co-intercalation

Engineering Contradiction:

ImproveflammabilityVSAvoidcompatibility with graphite anode

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The ionic liquid cation is modified with specific functional groups (fluorinated alkyl chains, aromatic moieties, ether linkages) at localized positions to create regions with different chemical properties. These local modifications prevent cationic co-intercalation into graphite while maintaining overall non-flammability and ionic conductivity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates composite ionic liquid structures combining multiple functional groups (e.g., fluorinated chains with aromatic rings, or ionic liquid cations with crown ether moieties) to achieve multiple functions simultaneously: non-flammability, graphite compatibility, and adequate ionic conductivity.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If ionic liquids are used as electrolytes, then thermal stability is improved, but lithium transference number deteriorates leading to polarization

Engineering Contradiction:

Improvethermal stabilityVSAvoidlithium transference number

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent systematically varies parameters of the ionic liquid cation including chain length, branching structure, aromatic content, and functional group types to optimize the balance between thermal stability and lithium ion mobility. Specific parameter ranges are identified to achieve both goals.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If ionic liquids are used as electrolytes, then non-flammability is improved, but ionic conductivity at low temperatures deteriorates

Engineering Contradiction:

ImproveflammabilityVSAvoidionic conductivity at low temperature

Core Design Contradiction:

Object-affected harmful factorsVSSpeed

Solution Approach 1:

The patent introduces intermediary substances including co-solvents (carbonates, carboxylic acid esters), nanoparticle additives (silica, alumina, titania), and film-forming additives that mediate between the ionic liquid and graphite anode. These intermediaries facilitate ion transport at low temperatures while maintaining the non-flammable nature of the ionic liquid base.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution enhances the compatibility and stability of ionic liquids with graphite anodes, improving ionic conductivity and preventing exfoliation, thereby extending the cycle life and discharge capacity of lithium-ion batteries.

Implementation Method 1

promotes stable surface electrolyte interphase formation with graphite anodes

Methodology Applied

Scientific EffectSurface electrolyte interphase formation:

Implementation Method 2

good room-temperature ionic conductivity

Methodology Applied

Scientific EffectIonic conductivity: Conduction (electrical)

Data Source

PatentUS10505227B2Functionalized ionic liquid combinations

Publication Date: 2019.12.10 SIONIC ENERGY INC

AI summary

This invention is directed to functional ionic liquid hybrid materials having negligible vapor pressure, nonflammability, good room-temperature ionic conductivity, wide electrochemical windows, and favorable chemical and thermal stability.