Lithium-ion Battery Electrolyte Ionic Liquid Optimization

Solution Overview

Problem

Lithium-ion batteries face challenges with flammability, discharge capacity, and stability due to the use of volatile and flammable organic solvents in their electrolytes, while previous attempts to reduce flammability using ionic liquids resulted in insufficient discharge voltage and capacity.

Innovation Solution

A lithium-ion battery design incorporating an electrolyte with a mixture of organic solvents, an ionic liquid with a weight percentage between 20% and 50%, and a passivation additive, along with a ceramic separator for improved wettability, which reduces flammability while maintaining high discharge voltage and capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ionic liquid weight percentage is increased to reduce flammability, then safety improves, but discharge capacity and voltage decrease

Engineering Contradiction:

ImprovesafetyVSAvoiddischarge capacity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies parameter changes by optimizing the ionic liquid concentration within a specific range (20-50% by weight) rather than using extreme values. This balanced parameter selection resolves the contradiction by achieving sufficient flammability reduction while maintaining adequate discharge capacity and voltage performance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by combining ionic liquids with conventional organic solvents (cyclic carbonates, chain carbonates, esters) in specific proportions. This composite electrolyte system integrates the safety benefits of ionic liquids with the good electrochemical performance of organic solvents, resolving the trade-off between safety and productivity.

Inventive Principle:

Principle #40Composite materials

2Reliability

If ionic liquid weight percentage is increased to reduce flammability, then safety improves, but discharge voltage decreases

Engineering Contradiction:

ImprovesafetyVSAvoiddischarge voltage

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent applies parameter changes by optimizing the ionic liquid concentration within a specific range (20-50% by weight) rather than using extreme values. This balanced parameter selection resolves the contradiction by achieving sufficient flammability reduction while maintaining adequate discharge voltage performance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by combining ionic liquids with conventional organic solvents (cyclic carbonates, chain carbonates, esters) in specific proportions. This composite electrolyte system integrates the safety benefits of ionic liquids with the good electrochemical performance of organic solvents, resolving the trade-off between safety and power.

Inventive Principle:

Principle #40Composite materials

3Productivity

If conventional organic solvents are used in electrolyte, then discharge capacity is maintained, but flammability increases

Engineering Contradiction:

Improvedischarge capacityVSAvoidflammability

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent uses composite materials by combining ionic liquids with conventional organic solvents (cyclic carbonates, chain carbonates, esters) in specific proportions. This composite electrolyte system integrates the safety benefits of ionic liquids with the good electrochemical performance of organic solvents, resolving the trade-off between productivity and harmful factors.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by allowing different solvent components to fulfill different functions: cyclic carbonates provide high dielectric constant for lithium salt dissolution, chain carbonates provide low viscosity for ion mobility, and ionic liquids provide flame suppression. Each component contributes locally to the overall performance, balancing capacity and safety.

Inventive Principle:

Principle #3Local quality

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 battery achieves reduced flammability, high discharge voltage, and stable capacity under cycling conditions, with optimal performance when the ionic liquid weight percentage is between 20% and 50%, ensuring safety and efficiency.

Implementation Method 1

The ionic liquids are characterized by a high thermal stability and a reduced flammability

Methodology Applied

Scientific EffectFlammability reduction:

Implementation Method 2

a passivation additive is added to the mixture of organic solvents, which forms a protective film on the surface of the negative electrode

Methodology Applied

Scientific EffectFilm formation:

Implementation Method 3

a separator, the apparent contact angle of which between its surface and the electrolyte is less than 20°

Methodology Applied

Scientific EffectWetting: Wetting

Implementation Method 4

Each positive electrode comprises an electrochemically active material capable of inserting lithium into its structure

Methodology Applied

Scientific EffectElectrochemical reaction:

Data Source

PatentUS9543617B2Lithium-ion battery containing an electrolyte comprising an ionic liquid

Publication Date: 2017.01.10 SAFT GRP SA

AI summary

A lithium-ion battery containing: a positive electrode, a negative electrode, an electrolyte comprising: an organic solvent chosen from the group comprising carbonates, linear esters of a saturated acid, or a mixture thereof, an additive capable of forming a passivation film on the surface of the negative electrode, at least one lithium salt, at least one ionic liquid for which the percentage by weight in the electrolyte is greater than or equal to 20% and less than 50%; a separator for which the apparent contact angle between the surface thereof and the electrolyte is less than 20°.