Fluorinated Electrolyte Additives for High-Voltage Li-Ion Cells
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Solution Overview
Problem
Lithium ion batteries face issues with electrolyte breakdown at high voltages, leading to poor performance and safety concerns, particularly when using high nickel cathodes like NMC 811 and silicon anodes.
Innovation Solution
The use of fluorinated ethers and carbonates, such as hexafluoroisopropyl methyl ether and trifluoromethylated carbonates, in the electrolyte to enhance the formation of a stable solid electrolyte interface (SEI) layer, combined with fluoroethylene carbonate, improves battery cycle life and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional carbonate and sulfite compounds are used as electrolyte solvents, then the electrolyte functions properly at normal voltages, but the electrolyte breaks down at battery voltages over 4.4 V, causing poor battery performance
Solution Approach 1:
The patent modifies the chemical structure of electrolyte compounds by introducing fluorinated groups (such as CF3 and CHF2) at specific positions in the molecular structure. This chemical parameter change increases the electrochemical stability window and resistance to breakdown at high voltages over 4.4 V, while maintaining the essential electrolyte functions of ion conductivity and SEI formation.
Solution Approach 2:
The patent employs composite electrolyte formulations combining fluorinated carbonate compounds (such as fluorinated dimethyl carbonate and fluorinated diethyl carbonate) with fluorinated sulfite compounds. This composite approach creates synergistic effects where the fluorinated carbonate provides stable SEI formation and the fluorinated sulfite enhances high-voltage stability, together achieving superior performance with high nickel cathodes like NMC 811.
2Use of energy by moving object
If high nickel cathodes like NMC 811 and silicon anodes are used, then energy density is improved, but electrolyte breakdown occurs leading to safety concerns and poor performance
Solution Approach 1:
The patent introduces fluorinated additives (such as fluorinated ethylene carbonate and fluorinated dimethyl carbonate) at specific concentration ranges (0.1-5% by weight) into the electrolyte formulation. These chemical parameter changes enable the electrolyte to form more stable SEI layers on silicon anodes and maintain stability with high nickel cathodes, allowing the battery to achieve high energy density while maintaining reliability and safety.
Solution Approach 2:
The fluorinated carbonate and sulfite compounds act as intermediary substances that mediate the interaction between the electrolyte and the high-voltage electrodes (NMC 811 cathode and silicon anode). These intermediaries form protective interface layers that prevent direct harmful interactions between the electrolyte and electrodes, enabling stable operation at high voltages and improving overall battery reliability while maintaining high energy density.
3Ease of manufacture
If conventional electrolytes are used with high voltage cathodes, then manufacturing is simple, but gassing occurs and cycle life is reduced
Solution Approach 1:
The patent modifies the electrolyte composition by incorporating fluorinated carbonate compounds (such as fluorinated dimethyl carbonate and fluorinated diethyl carbonate) and fluorinated sulfite compounds at optimized concentration ratios. These parameter changes suppress gassing reactions during charging cycles and improve the stability of the solid electrolyte interface, thereby extending battery cycle life while maintaining relatively simple manufacturing processes through conventional mixing and assembly methods.
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 significantly enhances the cycle life of batteries with high nickel cathodes and silicon anodes, reducing gassing and improving overall battery performance and safety.
Implementation Method 1
The use of fluorinated ethers and carbonates, such as hexafluoroisopropyl methyl ether and trifluoromethylated carbonates, in the electrolyte to enhance the formation of a stable solid electrolyte interface (SEI) layer
Implementation Method 2
at battery voltages over 4.4 V, these compounds break down and battery performance suffers as a result
Data Source
AI summary
The disclosure relates to the use of fluorinated ethers such as 1,1,1,3,3,3-hexafluoro-2-methoxypropane (HFMOP) as a reaction solvent to prepare fluorinated dialkyl carbonate and sulfite compounds useful in batteries, and to electrolytes containing fluorinated compounds for use in batteries containing high Ni cathodes and silicon containing anodes.