Azepanium Ionic Liquid Electrolyte for Li-Ion Battery Stability
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Solution Overview
Problem
Current ionic liquids used in Li-ion batteries suffer from poor cathodic stability, leading to co-intercalation and instability at graphite anodes, which limits their performance and safety.
Innovation Solution
The use of azepanium-based ionic liquids with specific functional moieties and anions, combined with aprotic organic solvents and alkali metal salts, to form stable and well-regulated layers at graphite surfaces, enhancing electrochemical and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure ionic liquids are used as electrolyte solvent, then thermal stability is improved, but viscosity increases and ionic conductivity decreases
Solution Approach 1:
The patent formulates a composite electrolyte containing azepanium-based ionic liquid (1-40 wt%), carbonate solvents (60-80 wt%), and lithium salts (1-10 wt%). This composite formulation balances the high thermal stability of pure IL with the low viscosity and high ionic conductivity of carbonate solvents, achieving optimal performance.
Solution Approach 2:
The patent optimizes the concentration parameter of azepanium IL in the electrolyte formulation (1-40 wt%), finding that this range provides sufficient thermal stability enhancement while maintaining acceptable viscosity and ionic conductivity through synergistic interaction with carbonate co-solvents.
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 approach improves the electrochemical stability and thermal stability of Li-ion batteries, allowing them to operate over a wider temperature range and maintain performance, reducing irreversible capacity loss and improving safety.
Implementation Method 1
During this process, the graphite electrode is cathodically polarized to low potential, and electrolyte solvent, salt anions and impurities in the electrolyte are reduced to form insoluble products that are deposited on the surface of the anode to form a passivating layer.
Implementation Method 2
electrolyte solvent, salt anions and impurities in the electrolyte are reduced to form insoluble products that are deposited on the surface of the anode
Implementation Method 3
The large cation size allows for delocalization and screening of charges, resulting in a reduction in the lattice energy and thereby the melting point or glass transition temperature.
Implementation Method 4
The large cation size allows for delocalization and screening of charges, resulting in a reduction in the lattice energy and thereby the melting point or glass transition temperature.
Implementation Method 5
Maolin et al. (Journal of Chemical Physics, 128, 134504, 2008), using molecular dynamic (MD) simulations of IL on a graphite surface, reported that the butyl group on the imidazolium cation aligned parallel to the graphite surface.
Data Source
AI summary
An ionic liquid compound includes an azepanium-functionalized cation. An electrochemical cell electrolyte for an electrical energy storage device includes the ionic liquid compound, aprotic organic solvent, alkali metal salt and an additive.