Anhydrous Fluoride Salt Electrolytes for Low-Temperature Ion Conductivity

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Solution Overview

Problem

Existing fluoride-ion battery systems face challenges due to poor ionic conductivity at low temperatures and the insolubility of metal fluorides in organic solvents, limiting their performance and application in electrochemical systems.

Innovation Solution

Development of anhydrous fluoride salts with organic cations that do not have a carbon in the β-position, combined with non-aqueous solvents, to create high-concentration fluoride-ion electrolyte solutions that promote dissociation and solubility, enhancing the performance of fluoride-ion batteries and other electrochemical applications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If solid-state electrolyte compositions are used in fluoride-ion batteries, then the battery structure is stable, but the ionic conductivity is poor at temperatures below 200°C, resulting in high cell internal resistance

Engineering Contradiction:

Improvebattery structure stabilityVSAvoidionic conductivity

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent changes the physical state parameter of the electrolyte from solid to liquid by using non-aqueous solvents with low freezing points. This allows the electrolyte to maintain high ionic conductivity at lower operating temperatures while preserving battery structure stability through the choice of appropriate solvent components.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite electrolyte system by combining non-aqueous solvents with specific fluoride salts. This composite approach enables the electrolyte to exhibit both the structural stability needed for battery operation and the high ionic conductivity required for power delivery, even at temperatures below 200°C.

Inventive Principle:

Principle #40Composite materials

2Reliability

If common metal fluorides are used as electrolyte components, then the battery can operate with fluoride ions, but these compounds are largely insoluble in organic solvents, limiting electrolyte options

Engineering Contradiction:

Improvefluoride ion conductivityVSAvoidelectrolyte solubility

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the chemical composition parameters of the electrolyte by selecting specific non-aqueous solvents and fluoride salt combinations. This enables high solubility of fluoride ions in the electrolyte solution, making it easy to manufacture while maintaining reliable fluoride ion conductivity for battery operation.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If lithium metal is used in battery systems, then the energy density is high, but lithium metal is highly reactive requiring safeguards that increase battery weight

Engineering Contradiction:

Improveenergy densityVSAvoidbattery weight

Core Design Contradiction:

Use of energy by moving objectVSWeight of moving object

Solution Approach 1:

The patent extracts lithium from the battery system by using fluoride-ion chemistry instead of lithium-based chemistry. This eliminates the need for lithium metal and its associated safety safeguards, reducing battery weight while maintaining high energy density through the fluoride-ion battery architecture.

Inventive Principle:

Principle #2Taking out (Extraction)

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 use of these anhydrous fluoride salts and non-aqueous solvents results in high fluoride-ion concentrations, improving the conductivity and solubility, thereby addressing the limitations of existing fluoride-ion battery systems and enabling their use in a wider range of electrochemical applications.

Implementation Method 1

Fluoride anions (F−) in the fluoride anion conducting electrolyte move from the cathode to the anode during discharge and from the anode to the cathode during charge of the battery

Methodology Applied

Scientific EffectIon transport: Electrolysis

Implementation Method 2

achieve efficient dissociation to generate high fluoride ion concentrations in non-aqueous solvents

Methodology Applied

Scientific EffectDissociation: Electrolysis

Data Source

PatentUS11830983B2Non-aqueous fluoride salts, solutions, and their uses

Publication Date: 2023.11.28 HONDA MOTOR CO LTD

AI summary

Electrolyte solutions including at least one anhydrous fluoride salt and at least one non-aqueous solvent are presented. The fluoride salt includes an organic cation having a charge center (e.g., N, P, S, or O) that does not possess a carbon in the β-position or does not possess a carbon in the β-position having a bound hydrogen. This salt structure facilitates its ability to be made anhydrous without decomposition. Example anhydrous fluoride salts include (2,2-dimethylpropyl)trimethylammonium fluoride and bis(2,2-dimethylpropyl)dimethylammonium fluoride. Combining these fluoride salts with at least one fluorine-containing non-aqueous solvent (e.g., bis(2,2,2-trifluoroethyl)ether; (BTFE)) promotes solubility of the salt within the non-aqueous solvents. The solvent may be a mixture of at least one non-aqueous, fluorine-containing solvent and at least one other non-aqueous, fluorine or non-fluorine containing solvent (e.g., BTFE and propionitrile or dimethoxyethane). The electrolyte solutions may be employed in electrochemical cells, such as batteries, fuel cells, electrolysis systems, and capacitors.