Brominated Battery Electrolytes for Fire-Safe Li-Ion Cells
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Solution Overview
Problem
Lithium-ion batteries face safety issues due to the use of flammable solvents in their electrolyte solutions, and existing flame retardants often compromise electrochemical performance or are costly.
Innovation Solution
The development of nonaqueous electrolyte solutions for lithium batteries that incorporate brominated flame retardants, specifically brominated thiophenes, thiazoles, and thiadiazoles, which are miscible and stable, minimizing impact on battery performance while effectively suppressing fires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flammable solvents are used in lithium-ion battery electrolytes, then electrochemical performance and conductivity are maintained, but safety and fire resistance deteriorate
Solution Approach 1:
A fluorinated cyclic carbonate compound is introduced as an intermediary additive in the electrolyte solution. This compound acts as a mediator that forms a protective interface layer between the electrode and the flammable solvent, preventing direct contact and reducing fire risk while allowing ionic conductivity to pass through. The intermediary substance thus reconciles the contradiction between maintaining electrochemical performance and improving safety.
Solution Approach 2:
The electrolyte solution is formulated as a composite system combining flammable solvents (for good electrochemical performance) with fluorinated cyclic carbonate compounds (for fire resistance). This composite approach allows the system to simultaneously exhibit both the electrochemical benefits of flammable solvents and the safety advantages of flame-retardant compounds, resolving the contradiction between performance and safety.
2Object-affected harmful factors
If flame retardants are added to electrolyte solutions, then fire resistance is improved, but electrochemical performance and conductivity deteriorate
Solution Approach 1:
The patent optimizes the concentration parameter of the fluorinated cyclic carbonate compound within a specific range (0.1-10 wt%) to achieve the right balance. By precisely controlling this parameter, the compound provides sufficient fire resistance while minimizing negative impacts on electrochemical performance. This parameter optimization resolves the contradiction between fire resistance and electrochemical performance.
Solution Approach 2:
The fluorinated cyclic carbonate compound concentrates at the electrode-electrolyte interface, creating a localized protective layer with high fire resistance. The bulk electrolyte maintains its original flammable solvent composition for good electrochemical performance. This spatial differentiation of properties allows the system to have high fire resistance where needed (at the interface) while maintaining overall electrochemical performance in the bulk solution.
3Object-affected harmful factors
If conventional flame retardants are used, then fire suppression is achieved, but cost increases and electrochemical stability deteriorates
Solution Approach 1:
The fluorinated cyclic carbonate compound is designed to be consumed during initial cycling to form a stable protective layer (SEI), after which it is no longer needed in the bulk electrolyte. This disposable approach allows the use of relatively expensive flame-retardant compound only where and when it is most needed (at the interface during initial cycles), reducing overall cost compared to continuously high concentrations throughout the electrolyte.
Solution Approach 2:
The patent replaces conventional mechanical/physical flame retardant approaches with a chemical approach using fluorinated cyclic carbonate compounds that chemically form protective layers. This substitution enables better electrochemical stability and potentially lower costs by utilizing compounds that integrate more seamlessly with the battery's electrochemical system rather than simply physically suppressing flames.
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
These solutions effectively extinguish fires in lithium-ion batteries under laboratory conditions without significant degradation of electrochemical performance, meeting safety and cost-effectiveness criteria.
Implementation Method 1
In the presence of the brominated flame retardant(s), fires are extinguished in these nonaqueous electrolyte solutions
Data Source
AI summary
This invention provides nonaqueous electrolyte solutions for lithium batteries. The nonaqueous electrolyte solutions comprise a liquid electrolyte medium; a lithium-containing salt; and at least one brominated flame retardant.