Perfluorinated Ether Electrolyte for Lithium Battery Safety

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Solution Overview

Problem

Lithium secondary batteries face challenges in high-voltage and high-temperature environments due to electrolyte oxidation, leading to reduced lifespan and safety issues, particularly with carbonate-based solvents that are flammable and volatile, and perfluoro-based solvents that have low miscibility with lithium salts.

Innovation Solution

A lithium secondary battery electrolyte composition incorporating a perfluorinated ether-based solvent, fluoroethylene carbonate, and ethylmethyl carbonate, with a lithium salt, to provide flame retardancy and improved miscibility, reducing viscosity and enhancing lithium ion mobility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If carbonate-based organic solvent is used as electrolyte, then lithium ion mobility is improved, but safety deteriorates due to flammability and thermal runaway

Engineering Contradiction:

Improvelithium ion mobilityVSAvoidsafety

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent uses a composite electrolyte system combining perfluorinated cyclic carbonate and chain carbonate solvents. The perfluorinated cyclic carbonate provides flame retardancy and thermal stability, while the chain carbonate maintains good lithium ion mobility. This composite approach resolves the contradiction between safety and ion mobility by integrating materials with complementary properties.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies the chemical structure parameters of the electrolyte by introducing perfluorinated groups into the cyclic carbonate component. This parameter change (fluorination) fundamentally alters the safety properties by raising the flash point and improving thermal stability, while the chain carbonate component compensates for any mobility reduction through its linear structure and low viscosity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If perfluoro-based solvent is used to improve flame retardancy, then safety is improved, but miscibility with lithium salts deteriorates

Engineering Contradiction:

Improveflame retardancyVSAvoidmiscibility with lithium salts

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent creates a composite solvent system where perfluorinated cyclic carbonate (providing flame retardancy) is combined with chain carbonate (providing good salt miscibility). The chain carbonate acts as a compatibility enhancer that maintains lithium salt dissolution while the perfluorinated component delivers the desired safety improvements.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by having different solvent components perform different functions: the perfluorinated cyclic carbonate specifically targets flame retardancy and thermal stability in the high-voltage cathode environment, while the chain carbonate handles lithium salt solvation and ion transport. This functional differentiation resolves the contradiction between safety and miscibility.

Inventive Principle:

Principle #3Local quality

3Reliability

If electrolyte is oxidized at high voltage to form resistive layer, then voltage resistance is improved, but electrolyte depletion occurs causing lifespan deterioration

Engineering Contradiction:

Improvevoltage resistanceVSAvoidlifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent changes the chemical composition parameters by using perfluorinated cyclic carbonate instead of conventional carbonate solvents. The perfluorinated structure has higher oxidation resistance and forms more stable protective films at high voltage, reducing continuous electrolyte decomposition. This parameter change improves voltage resistance while minimizing electrolyte depletion, thereby extending battery lifespan.

Inventive Principle:

Principle #35Parameter changes

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 composition achieves excellent output and lifespan characteristics, improves safety by preventing thermal runaway, and maintains performance in high-temperature, high-voltage conditions, making it suitable for large- or medium-sized batteries in electric vehicles.

Implementation Method 1

To inhibit such as combustion reaction, a perfluoro-based solvent may be used to impart flame retardancy thereto

Methodology Applied

Scientific EffectFlame retardancy:

Implementation Method 2

low miscibility with same salts and precipitation of the lithium salts caused thereby

Methodology Applied

Scientific EffectMiscibility:

Implementation Method 3

reducing viscosity and enhancing lithium ion mobility

Methodology Applied

Scientific EffectViscosity reduction:

Data Source

PatentUS11450887B2Electrolyte for lithium secondary battery and lithium secondary battery containing same

Publication Date: 2022.09.20 HYUNDAI MOTOR CO LTD

AI summary

Disclosed herein are an electrolyte for a lithium secondary battery and a lithium secondary battery including the same. The disclosed lithium secondary battery includes: a cathode; an anode; a separator interposed between the cathode and the anode; and an electrolyte, wherein the electrolyte includes: a lithium salt; and a solvent including a perfluorinated ether-based solvent, fluoroethylene carbonate (FEC), and ethylmethyl carbonate (EMC).