Fluorinated Dioxaphospholane Additive for Lithium Battery Electrolyte
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Solution Overview
Problem
Phosphoric acid-based retardants used in lithium rechargeable batteries cause severe reductive decomposition at the negative electrode interface, reducing available capacity and increasing cell resistance, and excessive addition negatively impacts cycle-life characteristics.
Innovation Solution
A non-aqueous electrolyte comprising an organic solvent, a lithium salt, and a compound like 4,5-dimethyl-2-[(2,2,3,3-tetrafluoropropyl)oxy]-1,3,2-dioxaphospholane 2-oxide, which acts as a flame retardancy additive, reducing exothermic heat and improving cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If phosphoric acid-based retardant is added to improve flame retardancy, then flame resistance is improved, but reductive decomposition occurs at the negative electrode interface causing capacity loss and increased resistance
Solution Approach 1:
The patent extracts the harmful phosphoric acid-based retardant from the electrolyte composition and replaces it with a fluorinated cyclic carbonate compound. This removal eliminates the reductive decomposition problem at the negative electrode interface while maintaining flame retardancy through the alternative additive's different chemical properties.
Solution Approach 2:
The patent changes the chemical composition parameters by introducing a fluorinated cyclic carbonate compound with specific molecular structure (Formula 1) and controlling its concentration (0.1-10 wt%). This parameter change achieves flame retardancy without the harmful side effects of phosphoric acid-based retardants, as the fluorinated structure provides different reactivity characteristics.
2Object-affected harmful factors
If phosphoric acid-based retardant is added in excessive amount to improve flame retardancy, then flame resistance is improved, but cycle-life characteristics are significantly decreased
Solution Approach 1:
The patent optimizes the concentration parameter of the flame retardant additive to a specific range (0.1-10 wt%). This parameter optimization achieves effective flame retardancy while avoiding the excessive concentration that would cause cycle-life degradation, demonstrating the importance of precise compositional control.
Solution Approach 2:
The patent employs a small amount of fluorinated cyclic carbonate compound as a sacrificial additive that forms protective films on electrode surfaces. This additive is consumed in controlled amounts to create stable interface layers that improve both flame safety and long-term cycling performance.
3Reliability
If conventional electrolyte composition is used to maintain good electrochemical performance, then battery performance is maintained, but flame retardancy is insufficient
Solution Approach 1:
The patent creates a composite electrolyte system by combining conventional carbonate solvents (EC, DEC, EMC) and lithium salts with a fluorinated cyclic carbonate compound. This composite composition integrates the electrochemical benefits of conventional electrolytes with the flame retardancy properties of the fluorinated additive, achieving both performance and safety.
Solution Approach 2:
The fluorinated cyclic carbonate compound acts as an intermediary substance that mediates between the electrolyte and electrode interfaces. It forms protective films that prevent direct contact between harmful phosphoric acid-based retardants and electrode materials, thereby maintaining electrochemical performance while providing flame safety.
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 electrolyte solution enhances flame retardancy, lowers viscosity, improves initial irreversible efficiency, and extends cycle-life characteristics of lithium rechargeable batteries while maintaining excellent battery performance.
Implementation Method 1
a compound represented by Chemical Formula 1... which acts as a flame retardancy additive, reducing exothermic heat
Implementation Method 2
it suppresses a smooth intercalation reaction of lithium ions
Implementation Method 3
One or more lithium salts dissolved in a carbonate-based solvent has been generally used as an electrolyte
Data Source
AI summary
In one aspect, a rechargeable lithium battery comprising a non-aqueous electrolyte including an organic solvent; a lithium salt and a substituted 2-fluoroalkoxy-1,3,2-dioxaphospholane 2-oxide is provided. The 2-fluoroalkoxy-1,3,2-dioxaphospholane 2-oxide can be a compound represented by the following Chemical Formula 1.