Lithium Battery Electrolyte Difluorophosphite Additive High Temperature Stability

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Solution Overview

Problem

Lithium secondary batteries face issues with irreversible side reactions between the electrolyte and electrodes at high temperatures, leading to passivation film formation, reduced cycle life, and potential swelling and explosion due to decomposition of carbonate-based solvents.

Innovation Solution

An electrolyte composition for lithium secondary batteries incorporating a non-aqueous organic solvent, a lithium salt, and an additive with a compound represented by Chemical Formula 1, which includes a difluorophosphite group, is used to form a rigid solid electrolyte interface (SEI) film and prevent oxidation reactions, enhancing ion conductivity and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a conventional electrolyte with carbonate-based solvent is used, then the battery can operate at high temperature, but irreversible side reactions occur leading to passivation film formation and reduced cycle life

Engineering Contradiction:

Improvehigh temperature operationVSAvoidcycle life

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The difluorophosphite compound acts as an intermediary substance that mediates between the electrolyte and electrode at high temperatures. It forms a protective interface layer that prevents direct harmful interactions between the carbonate-based electrolyte and electrode materials, enabling high-temperature operation while maintaining cycle life through this protective intermediary layer

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameters of the electrolyte by introducing a difluorophosphite compound with specific molecular structure (Formula 1). This parameter change modifies the electrolyte's chemical properties to be more stable at high temperatures, preventing the irreversible side reactions that normally occur with conventional carbonate-based electrolytes

Inventive Principle:

Principle #35Parameter changes

2Temperature

If carbonate-based solvent is used in electrolyte, then the battery can function at high temperature, but decomposition occurs leading to gas generation and swelling

Engineering Contradiction:

Improvehigh temperature stabilityVSAvoidgas generation and swelling

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The invention converts the potential harm of high-temperature electrolyte decomposition into a benefit by using the difluorophosphite compound to form a stable protective layer first. This layer prevents the carbonate solvent from decomposing at high temperatures, thereby converting what would be a harmful decomposition process into a beneficial protective mechanism that prevents gas generation and swelling

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Device complexity

If no protective additive is added, then the electrolyte composition is simple, but oxidation reactions occur reducing battery durability

Engineering Contradiction:

Improveelectrolyte composition complexityVSAvoiddurability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The difluorophosphite compound serves as a protective intermediary that forms an interface layer between the electrolyte and electrode. This intermediary layer prevents oxidation reactions without requiring complex multi-component additive packages, maintaining relative simplicity in electrolyte composition while significantly improving durability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention creates a composite protective interface layer formed by the difluorophosphite compound on the electrode surface. This composite structure combines the electrolyte components with the protective additive to form a new interface material that resists oxidation and improves overall battery durability

Inventive Principle:

Principle #40Composite materials

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 proposed electrolyte composition significantly improves cycle-life characteristics and reduces gas generation at high temperatures, preventing swelling and enhancing the overall stability and performance of lithium secondary batteries.

Implementation Method 1

incorporating a non-aqueous organic solvent, a lithium salt, and an additive with a compound represented by Chemical Formula 1, which includes a difluorophosphite group, is used to form a rigid solid electrolyte interface (SEI) film and prevent oxidation reactions

Methodology Applied

Scientific EffectSolid electrolyte interface (SEI) film formation:

Implementation Method 2

lithium salts dissolved in the non-aqueous organic solvent are used as an electrolyte

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Data Source

PatentEP3522287B1Electrolyte for lithium secondary battery, and lithium secondary battery comprising the same

Publication Date: 2022.11.02 SAMSUNG SDI CO LTD

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AI summary

The present invention relates to an electrolyte for a lithium secondary battery, and a lithium secondary battery comprising the electrolyte, the electrolyte comprising a non-aqueous organic solvent; lithium salt; and an additive comprising a compound which contains a difluorophosphate (-PF2) group which is expressed by a particular chemical formula.