Pentacyclic Anion Salt for High-Voltage Lithium Battery Electrolytes
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Solution Overview
Problem
Current electrolytes for lithium batteries face challenges with stability at high temperatures and potentials greater than 4 V vs. Li+, as well as corrosion issues with aluminum electrodes, limiting their use in advanced electrochemical devices.
Innovation Solution
Development of ionic compounds with specific cations and anions, such as those derived from the formula -CFZ'Z', which provide enhanced conductivity and electrochemical stability, preventing aluminum corrosion and enabling operation beyond 4 V.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte salts are used, then good conductivity is achieved, but stability at high potentials greater than 4 V vs. Li+ deteriorates
Solution Approach 1:
The patent modifies the chemical structure of the anion by introducing fluorinated groups (-CF3, -CF2H, -CF2Cl, -C2F5, -C3F7, -C4F9) at specific positions of the dicyan imidazole ring. This structural parameter change increases the electrochemical stability window to beyond 4.5 V vs. Li+, resolving the contradiction between maintaining conductivity and achieving stability at high potentials.
Solution Approach 2:
The invention creates a composite anion structure combining the dicyan imidazole core with various fluorinated substituents. This composite structure integrates the electronic properties of the aromatic ring with the electron-withdrawing effects of fluorinated groups, achieving both good conductivity and enhanced electrochemical stability simultaneously.
2Reliability
If conventional electrolyte salts are used, then operational conductivity is maintained, but stability at high temperatures deteriorates
Solution Approach 1:
The patent introduces fluorinated substituents with varying chain lengths and structures (from -CF3 to -C4F9) on the dicyan imidazole anion. These parameter changes in molecular structure enhance the thermal stability of the electrolyte salt, allowing stable operation at elevated temperatures while maintaining ionic conductivity.
3Reliability
If conventional electrolyte salts are used, then good ionic conductivity is achieved, but corrosion of aluminum electrodes occurs
Solution Approach 1:
The patent modifies the anion structure by adding fluorinated groups that increase the electron-withdrawing capability and delocalize the negative charge more effectively. This parameter change reduces the nucleophilicity of the anion, preventing corrosion attacks on aluminum electrodes while maintaining good ionic conductivity through the electrolyte.
4Reliability
If complex anion structures are used to improve stability, then electrochemical stability increases, but manufacturing complexity increases
Solution Approach 1:
The patent presents a segmented synthesis approach where the fluorinated groups are introduced as separate substituents on the dicyan imidazole core. This segmentation allows for modular synthesis, where different fluorinated groups can be added in a systematic manner, simplifying the overall manufacturing process despite the complexity of the final stable structure.
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 compounds exhibit superior conductivity and anodic stability, preventing aluminum corrosion and allowing safe operation in lithium batteries and other electrochemical devices, with potential for industrial-scale production using affordable starting materials.
Implementation Method 1
The anions which serve as a countercharge to the cations are chosen from those which have a delocalized negative charge, because aprotic electrolytes cannot form hydrogen bonds with negative charges, and delocalization is the only way to obtain appreciable dissociation in These conditions.
Implementation Method 2
The solutes intended to provide the ionic type conductivity required for the electrolytes are chosen from metallic salts and from so-called 'ium' salts
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a pentacyclic anion salt and its use in electrolyte compositions. The compound comprises an inorganic, organic, or organometallic cation M of valence m (1≤m≤3), and m anions conforming to the formula in which Rf is a -CFZ'Z" group in which Z' is F or a perfluoroalkyl group having from 1 to 3 carbon atoms, and Z" is an H, F, Cl group, an alkoxy group possibly fluorinated or perfluorinated having from 1 to 5 carbon atoms, an oxalkoxy group possibly fluorinated or perfluorinated having from 1 to 5 carbon atoms, or an alkyl group possibly fluorinated or perfluorinated having from 1 to 5 carbon atoms; Z" being different from F when Z' is F. An electrolyte composition comprises said salt in solution in a liquid solvent or a polymer solvent.