Ionic Liquid Electrolyte for Conductive Anode Film Stability
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Solution Overview
Problem
Conventional ionic liquids and DMSF-based electrolytes face issues with reductive decomposition of cations forming high-resistance films on anodes and oxidative decomposition of anions leading to performance deterioration in lithium secondary batteries.
Innovation Solution
The development of an ionic liquid with a cationic portion represented by Chemical Formula 1 and an anionic portion, which is derived from converting DMSF into an ionic liquid, allowing for the formation of a film with high ionic conductivity on the anode while delaying oxidative decomposition of anions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ionic liquids with PYR12O1+ cations and FSI- anions are used, then high thermal stability and non-volatility are achieved, but reductive decomposition of cations occurs easily due to low LUMO energy level, forming high-resistance films on the anode
Solution Approach 1:
The patent modifies the LUMO energy level parameter of the cation by changing its chemical structure (introducing electron-withdrawing groups like -SO2F, -CF3, -F) to increase the LUMO energy level, thereby reducing the tendency for reductive decomposition and preventing high-resistance film formation while maintaining thermal stability
Solution Approach 2:
The patent creates a composite ionic liquid system combining a specifically designed cation (with formula (1)) and anion, where the cation structure is optimized to have appropriate LUMO energy level, achieving both thermal stability and resistance to reductive decomposition through the synergistic combination of cation and anion properties
2Reliability
If DMSF-based electrolyte is used, then a film with high ionic conductivity is formed on the anode and lithium side reactions are suppressed, but oxidative decomposition of anions is accelerated due to weak binding to anions
Solution Approach 1:
The patent modifies the HOMO energy level parameter of the anion by changing its chemical structure (introducing electron-donating groups or adjusting the conjugation system) to decrease the HOMO energy level, thereby reducing the tendency for oxidative decomposition while maintaining high ionic conductivity through appropriate anion design
3Speed
If DMSF-based electrolyte is used, then rapid intercalation and deintercalation of lithium is induced, but performance deteriorates upon repeated charging and discharging due to anion decomposition
Solution Approach 1:
The patent optimizes the electrochemical stability window parameters by adjusting both cation LUMO energy level and anion HOMO energy level, creating a balanced ionic liquid system that provides both rapid lithium intercalation kinetics and long-term stability during repeated charging and discharging cycles
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
This ionic liquid solution achieves high thermal stability, non-volatility, and non-flammability, along with improved oxidation stability by forming a film with high ionic conductivity on the anode, thereby enhancing the performance and stability of lithium secondary batteries.
Implementation Method 1
the ionic liquid is capable of forming a film having high ionic conductivity on an anode upon reductive decomposition of cations contained therein
Implementation Method 2
delaying decomposition of anions
Data Source
AI summary
Disclosed are an ionic liquid, an electrolyte including the ionic liquid, and a lithium secondary battery including the same. The ionic liquid is capable of forming a film having high ionic conductivity on an anode upon reductive decomposition of cations contained therein, and delaying the decomposition of anions.