Reactive Ionic Liquids for Stable Lithium-Ion Battery Electrolytes
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Solution Overview
Problem
Current ionic liquids used in lithium ion batteries suffer from high viscosity leading to lower lithium ion conductivity, inadequate reductive stability, and sensitivity to hydrolysis, which limits their application in high-energy batteries and electric vehicles.
Innovation Solution
Development of reactive ionic liquids with reduction-stable organic cations and fluoroalkyl phosphate or fluoroalkyl phosphinate anions, which form a passivating yet permeable layer, enhancing oxidation stability and reducing corrosiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ionic liquids are used in lithium ion batteries, then thermal stability and safety are improved, but viscosity increases leading to lower lithium ion conductivity
Solution Approach 1:
The patent modifies the chemical structure of ionic liquids by changing the anion type from traditional BF4- or PF6- to fluoroalkyl phosphate anions (such as F3P(C2F5)3-), and adjusts cation structures to optimize the balance between viscosity and conductivity while maintaining thermal stability
Solution Approach 2:
The patent creates composite electrolyte systems combining ionic liquids with specific additives and uses composite cation-anion structures (e.g., pyrrolidinium or imidazolium cations combined with fluoroalkyl phosphate anions) to achieve both high stability and good conductivity
2Productivity
If imidazolium-based ionic liquids are used, then lithium ion conductivity is improved, but reductive stability becomes inadequate
Solution Approach 1:
The patent introduces functional groups with specific local properties (ester groups, cyano groups, carbonate groups) at specific positions on the cation structure to enhance reductive stability without significantly affecting overall conductivity
Solution Approach 2:
The patent changes the chemical composition parameters by incorporating reduction-stable cations with specific functional groups and matching them with fluoroalkyl phosphate anions to achieve both adequate reductive stability and acceptable conductivity
3Productivity
If AlCl4-based ionic liquids are used, then early battery performance is achieved, but sensitivity to hydrolysis and corrosiveness increase
Solution Approach 1:
The patent employs fluoroalkyl phosphate anions and cations with functional groups that create a chemically inert environment resistant to hydrolysis, eliminating the corrosive behavior associated with AlCl4-based ionic liquids while maintaining battery performance
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 reactive ionic liquids exhibit improved thermal and oxidation stability, forming a passivating layer that enhances lithium ion conductivity and reduces corrosiveness, addressing the limitations of existing ionic liquids in lithium ion batteries.
Implementation Method 1
ionic liquids which contain, on the organic cation, groups or substituents which are susceptible to electrochemical reduction
Implementation Method 2
lithium ion conductivity of the IL-based electrolyte
Data Source
AI summary
The invention relates to reactive ionic liquids containing organic cations with groups or substituents which are susceptible to electrochemical reduction and anions obtained from fluoroalkyl phosphates, fluoroalkyl phosphinates, fluoroalkyl phosphonates, acetates, triflates, imides, methides, borates, phosphates and/or aluminates, for use in electrochemical cells, such as lithium ion batteries and double-layer capacitors.