Fluorinated Carbonate Electrolyte for Low-Temperature Lithium Batteries

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Solution Overview

Problem

Conventional lithium-ion batteries (LIBs) exhibit poor performance at low temperatures due to the freezing of ethylene carbonate-based electrolytes and inadequate rate capability, limiting their use in cold regions and seasons.

Innovation Solution

The use of a fluorinated cyclic carbonate-based electrolyte system, including a fluorinated cyclic carbonate, a solid electrolyte interphase (SEI)-forming additive salt, and a metal fluorophosphate salt, which improves ionic conductivity and SEI formation, thereby enhancing battery performance at temperatures as low as -40°C.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ethylene carbonate (EC) is used as the main electrolyte solvent, then stable SEI layer formation is achieved at room temperature, but the electrolyte freezes at low temperatures below -20°C due to high melting point

Engineering Contradiction:

ImproveSEI layer stabilityVSAvoidelectrolyte freezing point

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent changes the chemical composition parameters of the electrolyte by replacing EC with fluorinated cyclic carbonates (FEC, DFEC) and fluorinated linear carbonates (FMPC, FDMC), which have lower melting points and maintain ionic conductivity at low temperatures while still forming stable SEI layers

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite electrolyte systems combining multiple fluorinated carbonate components (cyclic and linear) with specific ratios to achieve both low-temperature fluidity and stable SEI formation, leveraging the complementary properties of each component

Inventive Principle:

Principle #40Composite materials

2Reliability

If EC-based electrolyte is used, then adequate SEI formation occurs at room temperature, but capacity and rate capability drop sharply at low temperatures

Engineering Contradiction:

ImproveSEI layer formationVSAvoidbattery capacity and rate capability

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent modifies the electrolyte composition to include fluorinated cyclic and linear carbonates with optimal ratios, adding SEI-forming additives (LiDFOB, LiBF2(C2O4)2) and fluorinated compounds to enhance both SEI stability and ionic conductivity at low temperatures, thereby maintaining capacity and rate capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces intermediary substances (SEI-forming additive salts and fluorinated compounds) that mediate between the electrolyte and electrode interfaces, facilitating stable SEI formation while maintaining high ionic conductivity for sustained battery performance at low temperatures

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If conventional EC-based electrolyte is used, then good performance is achieved at room temperature, but severe degradation occurs at low temperatures

Engineering Contradiction:

Improvebattery performance at room temperatureVSAvoidbattery stability at low temperature

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent fundamentally changes the electrolyte composition from EC-based to fluorinated carbonate-based systems, adjusting the ratios of cyclic and linear fluorinated carbonates along with additive concentrations to optimize performance across both room temperature and low temperature conditions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite electrolyte formulations combining fluorinated cyclic carbonates, fluorinated linear carbonates, SEI-forming additives, and fluorinated compounds to achieve robust performance stability across wide temperature ranges while maintaining room temperature productivity

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 electrolyte system maintains capacity retention of at least 90% over 300 cycles and achieves high ionic conductivity of at least 2 mS cm−1 at -20°C to -40°C, significantly improving the low-temperature performance of lithium secondary batteries.

Implementation Method 1

a solid electrolyte interphase (SEI)-forming additive salt, where the SEI is a layer of material that forms between the anode and the electrolyte produced by breakdown of electrolyte compounds during electrochemical operation

Methodology Applied

Scientific EffectSolid electrolyte interphase (SEI) formation:

Implementation Method 2

The electrolyte includes a lithium hexafluorophosphate salt, 4-fluoro-1,3-dioxolan-2-one (FEC), a lithium difluoro (oxalato) borate salt (LiDFOB), and a fluorinated compound... wherein the electrolyte has an ionic conductivity of at least 2 mS cm−1 at a temperature of about −20° C. to about −40° C.

Methodology Applied

Scientific EffectIonic conductivity: Conduction (electrical)

Data Source

PatentUS20240363900A1Electrolytes for low temperature lithium batteries

Publication Date: 2024.10.31 UCHICAGO ARGONNE LLC

AI summary

An electrochemical cell configured to operate at low temperatures includes a cathode comprising a cathode active material, an anode comprising an anode active material, a separator disposed between the cathode and the anode, and an electrolyte. The electrolyte includes a fluorinated cyclic carbonate, a solid electrolyte interphase (SEI)-forming additive salt, a metal fluorophosphate salt, and a fluorinated organic compound.