Fluorinated Electrolyte Solvent Composition for Low-Temperature Battery Operation
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Solution Overview
Problem
Lithium secondary batteries and lithium ion capacitors face challenges in maintaining a liquid state and exhibiting excellent performance at extremely low temperatures, such as -40°C, due to freezing issues and degradation of physical properties like flash point, freezing point, electric conductivity, and viscosity across a wide temperature range from 60°C to -40°C.
Innovation Solution
A non-aqueous electrolytic solution with specific solvent compositions, including ethylene carbonate, propylene carbonate, dimethyl carbonate, fluorinated chain esters, and methyl ethyl carbonate, is developed, ensuring a flash point of 20°C or higher and electric conductivity of 8 mS/cm or more, preventing freezing at -40°C and enhancing battery performance across the temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional non-aqueous electrolytic solutions are used to achieve high voltage (4.2V or higher), then energy density is improved, but the solvent is partially decomposed and freezing occurs at low temperatures
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolytic solution by incorporating fluorinated cyclic carbonate compounds (15-30 vol%) and specific chain carbonate combinations, which changes the physical and chemical properties to resist freezing while maintaining high voltage stability
Solution Approach 2:
The patent creates a composite electrolytic solution system combining fluorinated cyclic carbonate (FEC, FPC), chain carbonates (DMC, DEC, EMC), and cyclic carbonates (EC, PC) in specific proportions, where each component contributes different properties: FEC/FPC provide low-temperature resistance and high-voltage stability, while chain carbonates ensure fluidity and ionic conductivity
2Adaptability or versatility
If the operating temperature range is extended to include very low temperatures (-40°C or lower), then adaptability is improved, but the electrolytic solution freezes
Solution Approach 1:
The patent changes the compositional parameters by introducing fluorinated cyclic carbonates and optimizing the ratio of chain to cyclic carbonates, which lowers the freezing point and maintains liquid state stability across the -40°C to 60°C temperature range
Solution Approach 2:
The patent assigns different functional roles to different solvent components: fluorinated cyclic carbonates provide low-temperature fluidity, chain carbonates provide overall fluidity and ionic mobility, while cyclic carbonates provide high-voltage stability, creating a synergistic system with uniform performance across the temperature range
3Adaptability or versatility
If the operating temperature range is extended to include high temperatures (60°C or higher), then adaptability is improved, but physical properties such as flash point, freezing point, electric conductivity, and viscosity are degraded
Solution Approach 1:
The patent optimizes the compositional parameters including the ratio of fluorinated cyclic carbonate to chain carbonate (15-30 vol% vs. 40-60 vol%) and the concentration of lithium salt (0.5-2.0 mol/L), which maintains stable physical properties across the temperature range by balancing ionic conductivity, viscosity, and thermal stability
Solution Approach 2:
The patent develops a composite electrolytic solution where fluorinated cyclic carbonates enhance high-temperature stability and flash point, chain carbonates maintain ionic conductivity and reduce viscosity, and cyclic carbonates provide voltage stability, creating a synergistic system that resists physical property degradation at high temperatures
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 solution maintains a liquid state and improves battery performance, including withstand voltage and electric conductivity, ensuring excellent properties in lithium secondary batteries and lithium ion capacitors across a wide temperature range.
Implementation Method 1
the non-aqueous electrolytic solution being free from freezing even at a temperature as very low as −40° C.
Implementation Method 2
a non-aqueous electrolytic solution for a lithium secondary battery or a lithium ion capacitor, including a lithium salt as dissolved in a non-aqueous solvent
Data Source
AI summary
The present invention provides a non-aqueous electrolytic solution for a lithium secondary battery or a lithium ion capacitor, wherein the non-aqueous electrolytic solution includes a lithium salt as dissolved in a non-aqueous solvent in a concentration of 0.8 to 1.5 M (mol/L), the non-aqueous solvent includes, in relation to the whole of the non-aqueous solvent, 5 to 25% by volume of ethylene carbonate, 5 to 25% by volume of propylene carbonate, 20 to 30% by volume of dimethyl carbonate, 20 to 40% by volume of methyl ethyl carbonate, and 10 to 20% by volume of a fluorinated chain ester; the total content of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 20 to 30% by volume, the total content of dimethyl carbonate and the fluorinated chain ester in the non-aqueous solvent is 30 to 40% by volume; and the flash point of the non-aqueous electrolytic solution is 20° C. or higher, and the present invention also provides an energy storage device.