Lithium-Ion Electrolyte Flash Point and Ionic Conductivity
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Solution Overview
Problem
Current electrolytes for lithium-ion batteries face challenges in achieving high safety, performance, and longevity due to issues such as low flash points, toxic decomposition products, high flammability, and reduced lithium ion mobility, which are not adequately addressed by existing solutions like organic carbonates, solid electrolytes, gel polymer electrolytes, or ionic liquids.
Innovation Solution
A mixture of cyclic carbonates and sulfone derivatives with a lithium source as a conductive salt, which provides a high flash point above 85°C, improved ionic conductivity, and enhanced stability, while maintaining high cell performance even at elevated charge and discharge rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic carbonates are used as electrolyte, then ionic conductivity is improved, but flash point decreases and flammability increases
Solution Approach 1:
The patent uses a composite electrolyte system combining cyclic carbonate (EC) and sulfone derivative (DMSO) in specific ratios (95:5 to 50:50 by weight), creating a composite material that leverages the high ionic conductivity of carbonates while the sulfone derivative elevates the flash point above 85°C, thus resolving the contradiction between conductivity and flammability
Solution Approach 2:
The patent changes the chemical composition parameters by introducing sulfone derivatives as additives (5-50 wt%) to modify the electrolyte's physical properties, specifically raising the flash point while maintaining ionic conductivity through optimized concentration ratios of the components
2Object-affected harmful factors
If ionic liquids are used as electrolyte additive, then safety is improved, but lithium ion mobility decreases
Solution Approach 1:
The patent replaces expensive ionic liquids with a cost-effective sulfone derivative (DMSO) that provides similar safety benefits (flash point >85°C) without the severe mobility reduction, achieving a practical compromise between safety and performance at lower cost
Solution Approach 2:
The patent optimizes the concentration of sulfone derivative (5-50 wt%) to achieve the minimum effective amount for safety improvement while minimizing the negative impact on lithium ion mobility, thus resolving the contradiction between safety enhancement and ion transport
3Object-affected harmful factors
If sulfolane is used as electrolyte component, then flash point is improved, but viscosity increases
Solution Approach 1:
The patent extracts the essential safety function (flash point elevation) from sulfolane and achieves it through a different chemical approach using DMSO, which provides comparable flash point improvement without the severe viscosity penalty, thus separating the desired safety effect from the unwanted viscous effect
Solution Approach 2:
The patent creates a composite electrolyte where DMSO (sulfone derivative) combines with cyclic carbonate to achieve both high flash point and acceptable viscosity by leveraging the low-viscosity properties of carbonate to counterbalance the viscosity increase from the sulfone component
4Object-affected harmful factors
If flash point is increased above 85°C, then safety is improved, but cell performance may deteriorate
Solution Approach 1:
The patent systematically varies the composition ratio of cyclic carbonate to sulfone derivative (95:5 to 50:50 by weight) to find the optimal parameter range that simultaneously achieves flash point >85°C and maintains cell performance at 75% or more of available capacity, thus resolving the safety-performance trade-off
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 achieves a flash point of over 140°C without compromising cell performance at C rates up to 2C, ensuring both safety and efficiency, with specific capacities maintained at 75% of available capacity and sufficient lithium diffusion, while being non-toxic and cost-effective.
Implementation Method 1
high ionic conductivity, especially sufficient lithium-ion conductivity
Implementation Method 2
The cyclic carbonate and the sulfone derivative serve as solvents in which the conductive salts and additives are dissolved
Data Source
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AI summary
The invention relates to an electrolyte for lithium-ion batteries, comprising a mixture of ethylene carbonate (EC) and/or mono- or polyfluorinated ethylene carbonate, at least one sulfone derivative and at least one lithium source as a conducting salt, wherein the mixture has a flash point above 85°C. The invention further relates to the use of the electrolyte as an electrolyte in a lithium-ion cell and to a lithium-ion battery comprising the electrolyte.