LiFSI Electrolyte for Low-Temperature Lithium Battery Viscosity

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Solution Overview

Problem

Rechargeable lithium batteries used in electric vehicles face challenges with low temperature performance due to increased viscosity of solvents, affecting lithium ion mobility and battery output, especially in cold conditions.

Innovation Solution

An electrolyte composition including a combination of lithium salts such as LiPF6 and lithium bisfluorosulfonyl imide (LiFSI) at specific mole ratios, along with a non-aqueous organic solvent, which maintains low viscosity and high ion conductivity even at low temperatures, preventing current collector corrosion and enhancing battery performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the temperature drops close to the freezing point of the solvent, then the viscosity of the solvent rises drastically, but the mobility of lithium ions remarkably decreases

Engineering Contradiction:

Improvelow temperature outputVSAvoidviscosity increase

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters of the electrolyte by introducing LiFSI salt and specific additives (VC, FEC, GBL) in optimized concentrations. This modifies the physical properties of the electrolyte solution, specifically reducing its viscosity at low temperatures while maintaining ion conductivity, thereby resolving the contradiction between temperature and viscosity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite electrolyte system combining multiple lithium salts (LiPF6, LiFSI) and multiple solvents (EC, DEC, DMC, GBL) with specific additives. This composite formulation synergistically reduces viscosity at low temperatures while maintaining high ion mobility, solving the contradiction between temperature effects and viscosity

Inventive Principle:

Principle #40Composite materials

2Productivity

If the viscosity of the solvent rises drastically at low temperature, then the mobility of lithium ions remarkably decreases, but the battery output is affected

Engineering Contradiction:

Improvebattery outputVSAvoidion mobility

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent modifies the electrolyte composition parameters by adding LiFSI (0.05-0.5M) and specific additives in optimized amounts, which changes the viscosity-conductivity relationship of the electrolyte. This ensures high ion mobility is maintained even when temperature drops, thereby maintaining battery output and reliability simultaneously

Inventive Principle:

Principle #35Parameter changes

3Reliability

If conventional electrolyte compositions are used, then the battery can operate, but the current collector may corrode at high temperature

Engineering Contradiction:

Improvecurrent collector stabilityVSAvoidhigh temperature characteristics

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent introduces GBL (γ-butyrolactone) as an intermediary substance in the electrolyte composition (0.5-5 wt%). This additive acts as a mediator that forms protective films on the current collector surface, preventing direct contact between the electrolyte and the aluminum current collector, thereby preventing corrosion while maintaining high temperature operation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical composition parameters of the electrolyte by incorporating specific additives (VC, FEC, GBL) in optimized concentrations. These additives modify the interface chemistry between the electrolyte and current collector, creating a stable protective layer that prevents corrosion at high temperatures

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 improves low temperature output and high temperature characteristics by maintaining ion mobility and conductivity, reducing internal resistance and extending cycle-life, while ensuring the stability of the current collector.

Implementation Method 1

the mobility of lithium ions

Methodology Applied

Scientific EffectIon mobility: Conduction (electrical)

Implementation Method 2

the viscosity of the solvent rises drastically

Methodology Applied

Scientific EffectViscosity:

Implementation Method 3

the form of the solid electrolyte interface (SEI) formed on the surface of the negative electrode

Methodology Applied

Scientific EffectSolid electrolyte interface (SEI) formation:

Data Source

PatentUS9112237B2Electrolyte for rechargeable lithium battery and rechargeable lithium battery including same

Publication Date: 2015.08.18 SAMSUNG SDI CO LTD

AI summary

Disclosed is an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same, and the electrolyte includes a lithium salt composition including a first lithium salt; and a second lithium salt of lithium bisfluorosulfonyl imide represented by the following Chemical Formula 1 at a mole ratio of 1:0.05 to 1:1, and a non-aqueous organic solvent.