Ionic Liquid Battery Electrolyte With Cosolvents for Li-Ion Conductivity

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Solution Overview

Problem

Ionic liquids used in lithium secondary batteries have low lithium ion conductivity due to high viscosity, limiting their performance and lifespan.

Innovation Solution

A mixed solvent system comprising an ionic liquid and cosolvents, including carbonate-based and nitrile-based solvents, along with specific electrolyte salts, is employed to enhance ion conductivity and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ionic liquid is used as solvent, then electrochemical stability and non-flammable properties are improved, but lithium ion conductivity deteriorates due to high viscosity

Engineering Contradiction:

Improveelectrochemical stabilityVSAvoidlithium ion conductivity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent uses a composite solvent system combining ionic liquid (50-80 vol%) with carbonate-based solvent (5-45 vol%) and nitrile-based solvent (5-10 vol%). This composite approach allows the electrolyte to inherit electrochemical stability and non-flammability from the ionic liquid while the carbonate and nitrile solvents reduce viscosity to improve lithium ion conductivity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes the viscosity parameter by controlling the proportions of different solvents and adjusting temperature conditions. By changing the composition ratio parameters (specifically maintaining ionic liquid at 50-80 vol% while adding lower-viscosity cosolvents), the electrolyte achieves reduced viscosity and improved ion conductivity while preserving the stability benefits of ionic liquid.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If ionic liquid is used as solvent, then non-flammable properties are improved, but lithium ion conductivity deteriorates

Engineering Contradiction:

Improvenon-flammable propertiesVSAvoidlithium ion conductivity

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The electrolyte employs a composite solvent system where ionic liquid (50-80 vol%) provides non-flammable safety properties, while carbonate-based (5-45 vol%) and nitrile-based (5-10 vol%) solvents are added to reduce overall viscosity. This composite formulation maintains the fire safety advantage of ionic liquid while enabling sufficient ion conductivity for practical battery operation.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different solvent components perform specialized functions: the ionic liquid phase provides safety and stability, while the carbonate and nitrile phases locally reduce viscosity in regions where ion transport occurs. This local quality differentiation allows simultaneous achievement of non-flammability and adequate conductivity.

Inventive Principle:

Principle #3Local quality

3Temperature

If ionic liquid is used as solvent, then thermal stability is improved, but lithium ion conductivity deteriorates due to high viscosity

Engineering Contradiction:

Improvethermal stabilityVSAvoidlithium ion conductivity

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

The patent creates a composite electrolyte system where thermally stable ionic liquid (50-80 vol%) is combined with carbonate-based (5-45 vol%) and nitrile-based (5-10 vol%) solvents. The ionic liquid component maintains thermal stability, while the added cosolvents reduce viscosity to enable adequate lithium ion conductivity at operating temperatures.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The electrolyte composition is designed to dynamically adjust its viscosity characteristics based on temperature and composition ratios. By optimizing the ionic liquid content at 50-80 vol% and adding appropriate amounts of lower-viscosity cosolvents, the system achieves a dynamic balance between thermal stability and ion conductivity across different operating conditions.

Inventive Principle:

Principle #15Dynamics

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 electrolyte achieves high ion conductivity and electrochemical stability, improving the lifespan and performance of lithium secondary batteries.

Implementation Method 1

A mixed solvent including an ionic liquid and cosolvents, and at least one electrolyte salt

Methodology Applied

Scientific EffectSolvation: Solvation

Implementation Method 2

the ionic liquids have low lithium ion conductivity due to the high viscosity thereof

Methodology Applied

Scientific EffectViscosity reduction:

Implementation Method 3

The electrolyte achieves high ion conductivity and electrochemical stability

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 4

the ionic liquids have low volatility, thermal stability and electrochemical stability and non-flammable properties

Methodology Applied

Scientific EffectElectrochemical stability:

Data Source

PatentUS12586820B2Electrolyte for lithium secondary batteries comprising ionic liquid and cosolvent and lithium secondary battery comprising the same

Publication Date: 2026.03.24 HYUNDAI MOTOR CO LTD

AI summary

An electrolyte for lithium secondary batteries includes an ionic liquid and cosolvents and a lithium secondary battery includes the same. The electrolyte includes a mixed solvent including the ionic liquid and the cosolvents, and at least one electrolyte salt, the cosolvents include a carbonate-based solvent and a nitrile-based solvent, and the mixed solvent includes 50-80 vol % of the ionic liquid, 15-45 vol % of the carbonate-based solvent, and 5-10 vol % of the nitrile-based solvent.