Flame-Retardant Electrolyte Composition for Stable Li-Ion Battery Capacity
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Solution Overview
Problem
Lithium-ion batteries face safety issues due to the flammability of carbonate-based electrolytes, which can be improved with flame retardant additives but often result in battery performance degradation, particularly due to strong catalytic activity of graphite electrodes.
Innovation Solution
A flame-retardant electrolyte comprising a specific solvent mixture, lithium salt, and fluoroethylene carbonate, with a concentration range of 5-7 mol/kg lithium salt and a 10% mass ratio of fluoroethylene carbonate, which prevents lithium salt precipitation and enhances electrode stability, thereby improving safety without degrading battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If flame retardant additives are added to improve electrolyte safety, then flame retardancy is improved, but battery performance degrades
Solution Approach 1:
The patent changes the chemical composition parameters by introducing fluorinated cyclic carbonate compounds with specific molecular structures (FEC, FPC, FDC) and controlling their concentration ratios (5-20% by mass) in the electrolyte formulation. This parameter optimization achieves flame retardancy while maintaining battery performance through precise compositional control
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate compounds with conventional carbonate solvents (EC, PC, DEC, EMC, DMC) and lithium salts. This composite approach integrates the flame-retardant properties of fluorinated compounds with the electrochemical performance of conventional solvents, achieving both safety and performance goals
2Object-affected harmful factors
If conventional flame retardant additives are used, then electrolyte safety is improved, but electrode stability deteriorates due to strong catalytic activity of graphite
Solution Approach 1:
The fluorinated cyclic carbonate compounds act as intermediary substances that form stable protective films on graphite electrode surfaces. These films serve as mediators between the electrolyte and electrode, preventing direct harmful interactions while maintaining electrochemical functionality, thus protecting the electrode from catalytic degradation
Solution Approach 2:
The fluorinated cyclic carbonate compounds function as sacrificial additives that are consumed during initial cycles to form stable protective layers on electrodes. These compounds decompose preferentially to create stable SEI films, sacrificing themselves to protect the electrode from ongoing degradation, similar to disposable protective elements
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 proposed electrolyte solution provides a lithium-ion battery with enhanced flame retardancy and stability, maintaining discharge capacity above 200 mAh/g and low irreversibility, comparable to traditional batteries, while ensuring high energy and safety performance.
Implementation Method 1
The fluorinated solvent can avoid the precipitation of the lithium salt and improve the stability of a negative electrode of the lithium ion battery
Data Source
AI summary
The present application provides a flame-retardant electrolyte. The flame-retardant electrolyte includes a specific solvent; a lithium salt; and a fluorinated solvent. The specific solvent is carbonate solvent, ether solvent, succinonitrile, sulfolane, tetraglyme, ionic liquid or a combination thereof. Or, the flame-retardant electrolyte comprises 1-Butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl)imide, lithium salt, and carbonate solvent.