Phosphonium Ionic Liquid Electrolyte for Low-Temperature Battery Applications
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Solution Overview
Problem
There is a lack of ionic liquids that maintain a stable liquid state at low temperatures, have low viscosity, and exhibit high conductivity and electrochemical stability, limiting their application in rechargeable lithium batteries, electrical double layer capacitors, fuel cells, and dye sensitized solar cells.
Innovation Solution
The development of an ionic liquid with a cation component represented by a specific general formula, combined with suitable anion components such as (CF3SO2)2N-, PF6-, or BF4-, which provides low viscosity, adequate conductivity, and excellent electrochemical stability, enabling its use as an electrolyte or solvent in various energy storage devices and reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional ionic liquids containing nitrogen atom-containing onium cations are used, then they can be synthesized with relatively easy methods, but they only maintain liquid state at temperatures above 25°C and exhibit high viscosity at room temperature
Solution Approach 1:
The patent changes the chemical structure parameters of the cation from conventional nitrogen-containing onium cations to phosphonium cations with specific structural features (formula 1), which fundamentally alters the melting point and viscosity characteristics, enabling liquid state at lower temperatures while maintaining synthesizability
Solution Approach 2:
The patent creates composite ionic liquids by combining phosphonium cations with various anions (formula 2), where the specific combination of cation and anion structures achieves optimal balance between liquid state stability, viscosity, and electrochemical properties
2Reliability
If ionic liquids with low viscosity and melting point such as imidazolium cations are used, then they can be synthesized with ease, but they exhibit inadequate stability against reduction and narrow potential window
Solution Approach 1:
The patent changes the cation type from imidazolium to phosphonium with specific structural parameters (formula 1), which improves electrochemical stability and reduction resistance while maintaining low viscosity and reasonable synthesizability through established phosphonium salt preparation methods
3Reliability
If ionic liquids are designed to maintain stable liquid state at low temperatures with low viscosity, then they can achieve high conductivity, but there is a lack of ionic liquids with adequate electrochemical stability for energy storage applications
Solution Approach 1:
The patent designs composite ionic liquids by combining phosphonium cations (formula 1) with specific anions (formula 2), where the synergistic interaction between cation and anion structures achieves both low-temperature liquid state stability and high electrochemical stability required for energy storage applications
Solution Approach 2:
The patent optimizes specific local structural features within the phosphonium cation (substitution groups R1-R9 in formula 1) to achieve localized properties that contribute to overall electrochemical stability while maintaining low viscosity and high conductivity
Data Source
AI summary
An ionic liquid of the present invention is "an ionic liquid comprising an organic substance represented by the following general formula (1) as a cation component" and "an ionic liquid comprising a cation component and an anion component, and the cation component is one or plural kinds selected from the group consisting of cation components represented by the following formula (1)".