Fluorinated Solvent Electrolyte for High-Voltage Li-Ion Stability
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Solution Overview
Problem
Current lithium ion battery electrolytes decompose at cathode potentials above 4.2 V, leading to performance loss and gas generation, which causes battery swelling.
Innovation Solution
An electrolyte composition comprising a fluorinated solvent, an organic carbonate, a sultone, and an electrolyte salt, which minimizes gas formation while maintaining battery performance, is developed. The composition includes a fluorinated solvent represented by specific formulas, a sultone optionally substituted with halogen or alkyl groups, and an electrolyte salt, and may further include borates like lithium bis(oxalato)borate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solvents (linear carbonates and cyclic carbonates) are used, then good battery performance is achieved, but electrolyte decomposition occurs at cathode potentials above 4.2 V leading to gas formation and performance loss
Solution Approach 1:
The patent introduces fluorinated solvents with specific molecular structures (containing CF3 or CF2 groups) to change the chemical parameters of the electrolyte composition. This structural modification increases the electrochemical stability window and raises the decomposition potential above 4.2 V, thereby preventing gas formation while maintaining conductivity
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated solvents with conventional carbonates (EC, DMF, DMC) and lithium salts (LiPF6, LiBF4). This composite formulation synergistically combines the high stability of fluorinated compounds with the good ionic conductivity of conventional carbonates, achieving both gas suppression and performance maintenance
2Productivity
If electrolyte decomposition is prevented, then gas formation is reduced, but operational voltage capability must be increased to achieve higher energy density
Solution Approach 1:
The fluorinated solvent molecules contain electron-withdrawing fluorine atoms that stabilize the electrolyte against oxidation at high potentials. This chemical parameter change enables the electrolyte to withstand cathode potentials above 4.2 V, allowing operation at higher voltages for increased energy density without decomposition
Solution Approach 2:
The patent applies fluorine substitution at specific positions in the solvent molecules (creating CF3 or CF2 groups) to provide localized electron-withdrawing effects. This local chemical modification creates protective zones around the electrolyte molecules that resist decomposition at the cathode interface while maintaining bulk ionic conductivity
Data Source
AI summary
Described are electrolyte compositions comprising a fluorinated solvent, an organic carbonate, a sultone, and optionally a borate. The fluorinated solvent may be a fluorinated acyclic carboxylic acid ester, a fluorinated acyclic carbonate, a fluorinated acyclic ether, or mixtures thereof. The organic carbonate may be fluorinated or non-fluorinated. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries.