Phosphazene Electrolyte Additive for Fire-Safe Li-Ion Conductivity
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Solution Overview
Problem
Existing lithium-ion batteries face issues with high viscosity and reduced ion conductivity due to excessive phosphorus-containing compounds, leading to decreased rate performance and safety concerns, while commercially available fire-retarding additives like PFPN are costly and not economically viable.
Innovation Solution
A phosphazene derivative with a specific structure is introduced as an electrolyte additive, which improves safety and cycle performance without increasing process complexity, offering better fire-retardation than PFPN at a lower cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphorus-containing compounds are added to improve fire safety, then thermal safety is improved, but viscosity increases and ion conductivity decreases
Solution Approach 1:
The patent changes the chemical structure parameters of phosphorus-containing compounds by introducing fluorine atoms and cyclic phosphazene structures. This structural modification reduces the molecular size and steric hindrance compared to conventional phosphate compounds, allowing the additive to provide fire safety while minimizing viscosity increase and maintaining ion conductivity.
Solution Approach 2:
The patent uses composite electrolyte systems combining cyclic phosphazene derivatives with conventional carbonate solvents and lithium salts. This composite approach leverages the fire-retardant properties of phosphazene compounds while the carbonate base maintains good ion conductivity, achieving a balance between safety and performance.
2Reliability
If PFPN additive is used to improve fire-retardation, then safety is improved, but cost increases
Solution Approach 1:
The patent employs conventional phosphazene building blocks and standard organic solvents that are commercially available and relatively inexpensive. By using readily synthesizable compounds rather than specialized expensive additives like PFPN, the patent achieves fire-retardation at lower cost, making the electrolyte economically viable for commercial battery production.
3Reliability
If phosphorus-containing compounds are added to improve safety, then fire safety is improved, but rate performance decreases
Solution Approach 1:
The patent modifies the molecular parameters of phosphorus compounds by creating cyclic phosphazene structures with fluorine substitution. This structural change reduces molecular weight and increases molecular symmetry, which minimizes the impact on electrolyte viscosity and maintains fast ion transport kinetics, thereby preserving rate performance while providing fire safety.
Data Source
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AI summary
The present disclosure provides a phosphazene derivative, a composition for an electrochemical device and an electrochemical device containing the composition The composition includes an electrolyte, a non-aqueous solvent and an additive. The additive includes a phosphazene derivative of the formula (I), n, R1 and R2 are as defined herein: The safety characteristics of the electrochemical device provided in the present disclosure are improved by adding the aforementioned additives to the composition in the electrochemical device.