Fluorinated Cyclic Carbonate Additives for Stable SEI Formation
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Solution Overview
Problem
Conventional lithium ion batteries using graphite anodes face issues with solvent propylene carbonate leading to irreversible destruction due to reductive decomposition and lack of solid electrolyte interphase formation, limiting their utility and requiring high concentrations of electrolytes that decrease battery performance and energy density.
Innovation Solution
Incorporating compounds of the general formula (X = C, S, or S═O; R1 = CN, C1-C10-alkyl, C1-C10-alkoxy, C3-C7-cycloalkyl, C6-C10-aryl, or —CO—O—R2) as electrolyte additives, such as 3-methyl-1,4,2-dioxoazol-5-one, which form a stable solid electrolyte interphase (SEI) on graphite electrodes, enabling the use of solvents like propylene carbonate and enhancing oxidative stability for high-voltage applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If propylene carbonate is used as solvent in lithium ion batteries with graphite anodes, then thermal and physicochemical properties are improved, but reductive decomposition occurs leading to exfoliation and destruction of graphite
Solution Approach 1:
The patent introduces a mediator substance (fluorinated cyclic carbonate additive) that acts as an intermediary between propylene carbonate and graphite anode. This additive preferentially reacts with graphite to form a stable SEI layer, preventing direct harmful interaction between propylene carbonate and graphite, thus allowing propylene carbonate to be used while protecting the anode from exfoliation
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by adding fluorinated cyclic carbonate compounds with specific molecular structures (containing F, C, O atoms in cyclic arrangements). This parameter change in electrolyte composition enables the formation of a stable SEI layer that prevents graphite exfoliation while maintaining propylene carbonate's thermal benefits
2Reliability
If highly concentrated electrolytes are used to suppress exfoliation and reductive decomposition, then graphite stability is improved, but viscosity increases greatly leading to decreased conductivity and battery performance
Solution Approach 1:
Instead of changing concentration parameters (using highly concentrated electrolytes), the patent changes the chemical nature parameters by introducing fluorinated cyclic carbonate additives. This alternative parameter change achieves graphite protection through SEI formation without the detrimental viscosity increase and conductivity loss associated with high concentration electrolytes
Solution Approach 2:
The patent uses small amounts of fluorinated cyclic carbonate additive that are consumed during SEI formation. This additive acts as a sacrificial component that forms a stable protective layer, allowing the use of conventional low-concentration electrolytes that maintain good conductivity and performance
3Reliability
If highly concentrated electrolytes are used to suppress exfoliation, then graphite stability is improved, but density increases leading to decreased specific energy density
Solution Approach 1:
The patent changes from concentration-based protection (highly concentrated electrolytes increasing density) to composition-based protection (fluorinated cyclic carbonate additives). This parameter change in electrolyte formulation achieves graphite stability without significant density increase, preserving specific energy density
4Reliability
If conventional additives like vinylene carbonate are used, then SEI formation is improved, but oxidative decomposition occurs at voltages above 4.7 V limiting high-voltage applications
Solution Approach 1:
The patent changes the chemical structure parameters of the cyclic carbonate additive by introducing fluorine atoms. This parameter change in molecular composition (fluorination) increases oxidative stability, allowing SEI formation to occur at high voltages above 4.7 V without oxidative decomposition, enabling high-voltage battery applications
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 SEI formed by these compounds protects graphite anodes from exfoliation and bulk electrolyte from continuous reductive decomposition, allowing for stable operation over 50 charging and discharging cycles, and supports high-voltage battery performance with improved cycling stability and oxidative stability.
Implementation Method 1
In the case of graphite anodes, reductive decomposition of the electrolyte occurs and the reaction products can form an adhering film which is electronically insulating but conducts lithium ions on the anode
Implementation Method 2
The solid electrolyte interphase then prevents the electrode material from reacting further with the electrolyte and in this way protects the electrolyte from further reductive decomposition and the anode from destruction by the solvent
Implementation Method 3
the reaction products can form an adhering film which is electronically insulating but conducts lithium ions on the anode
Data Source
AI summary
The invention relates to the use of compounds according to general formula (1), in particular 1,4,2-dioxoazol-5-on-derivatives, as additives in electrolytes for electrochemical energy sources such as lithium-ion-batteries, and compounds containing electrolytes according to general formula (1), in particular 1,4,2-dioxoazol-5-on-derivatives.