Phosphazene Additive for Flame-Retardant Electrolyte

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Solution Overview

Problem

Non-aqueous electrolyte secondary batteries face safety concerns due to the high reactivity of alkali metals like lithium, which can lead to ignition, explosion, or excessive heat during short circuits or overcharge, and existing safety mechanisms like safety valves may not function reliably.

Innovation Solution

Incorporating a phosphazene compound with a hexafluoroisopropoxy group into the non-aqueous electrolyte to create a self-extinguishing, flame-retardant, and incombustible electrolyte that suppresses decomposition and corrosion, enhancing safety and battery characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If alkali metals (lithium metals or lithium alloys) are used as negative electrode material to achieve high voltage and energy concentration, then battery performance is improved, but safety deteriorates due to high reactivity with water and low melting point

Engineering Contradiction:

Improvevoltage and energy concentrationVSAvoidsafety

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A phosphazene compound with hexafluoroisopropoxy group is introduced as an intermediary substance in the electrolyte. This compound acts as a mediator between the lithium metal and the electrolyte environment, forming a protective interface layer that prevents direct contact and reaction between lithium and water or oxygen, thereby reducing safety hazards while maintaining high energy density

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electrolyte is formulated as a composite system containing the phosphazene compound with hexafluoroisopropoxy group combined with other electrolyte components. This composite electrolyte structure provides both the high ionic conductivity needed for performance and the flame-retardant properties needed for safety, resolving the contradiction between energy density and safety

Inventive Principle:

Principle #40Composite materials

2Reliability

If safety valves are installed to prevent excessive pressure and temperature during short circuit or overcharge, then safety mechanisms are provided, but reliability deteriorates because the mechanism may not operate normally

Engineering Contradiction:

Improvesafety mechanismVSAvoidsafety valve mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The phosphazene compound with hexafluoroisopropoxy group provides self-protective functionality to the battery system. When temperature rises or decomposition occurs, the compound inherently exhibits flame-retardant and pressure-regulating properties without requiring external safety valves or mechanical intervention, thereby eliminating complex safety mechanisms while maintaining or improving safety

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The mechanical safety valve system is replaced by chemical properties of the phosphazene compound. Instead of relying on mechanical pressure relief through a valve, the electrolyte itself provides pressure and temperature management through its inherent flame-retardant characteristics and decomposition behavior, substituting a mechanical safety system with a chemical safety mechanism

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If conventional electrolytes are used to achieve good battery characteristics, then performance is maintained, but safety deteriorates due to risk of evaporation, decomposition, ignition, and explosion under heat

Engineering Contradiction:

Improvebattery characteristicsVSAvoidevaporation, decomposition, ignition, explosion risk

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The chemical composition parameter of the electrolyte is changed by incorporating the phosphazene compound with hexafluoroisopropoxy group. This compositional change fundamentally alters the thermal and chemical stability parameters of the electrolyte, raising the decomposition temperature and eliminating flammability while maintaining ionic conductivity and battery performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The phosphazene compound with hexafluoroisopropoxy group creates an inert chemical environment within the battery. The compound's molecular structure and chemical properties provide an atmosphere that is resistant to oxidation, decomposition, and ignition, protecting the battery components from harmful reactions even under elevated temperature conditions

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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 phosphazene compound significantly improves safety by preventing ignition and explosion, while maintaining battery performance through reduced decomposition and corrosion, as evidenced by enhanced safety evaluation and charge-discharge cycle performance.

Implementation Method 1

suppresses decomposition and corrosion

Methodology Applied

Scientific EffectDecomposition suppression:

Implementation Method 2

self-extinguishing, flame-retardant, and incombustible electrolyte

Methodology Applied

Scientific EffectFlame retardation:

Data Source

PatentEP2683013B1Nonaqueous electrolyte additive, nonaqueous electrolyte, and nonaqueous electrolyte secondary battery

Publication Date: 2018.01.17 BRIDGESTONE CORP

AI summary

The present invention relates to a non-aqueous electrolyte additive that allows for improved safety and battery characteristics of a non-aqueous electrolyte secondary battery, and in greater detail, the present invention relates to a non-aqueous electrolyte additive that includes a phosphazene compound represented by the following general formula (1): (NPR2)n (1) wherein each R independently represents fluorine or a secondary or tertiary branched alkoxy group substituted with fluorine, at least one of the Rs represents the secondary or tertiary branched alkoxy group substituted with fluorine, and n is from 3 to 14.