Lithium Ion Electrolyte Solvent System for Low Temperature Conductivity
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Solution Overview
Problem
Current lithium ion battery technologies face limitations due to electrolyte deterioration and low flash points, which restrict operating temperatures and pose safety hazards, especially at elevated temperatures, and existing electrolytes have low conductivities and narrow electrochemical stability windows.
Innovation Solution
A novel electrolyte system comprising a lithium salt and a solvent system with a first aprotic solvent and a second fluorinated aprotic solvent, such as 3-fluorosulfolane, which enhances conductivity, flashpoint, and stability, allowing operation down to −40°C with reduced flammability and increased safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common non-aqueous polar co-solvents with high conductivity are used, then ionic conductivity is improved, but flash point decreases and fire hazard increases
Solution Approach 1:
The patent uses a composite solvent system combining multiple aprotic solvents (cyclic carbonates like EC and PC, chain carbonates like DMC and DEC, and cyclic carboxylic acid esters like GMC) in specific ratios. This composite approach allows the electrolyte to achieve high ionic conductivity (≥0.0084 S/cm at −40°C) while maintaining high flash point (≥160°C) by leveraging the complementary properties of each solvent component.
2Object-affected harmful factors
If cyclic carbonates like propylene carbonate and ethylene carbonate are used, then flash point and dielectric constant are improved, but low-temperature conductivity decreases and power density is limited
Solution Approach 1:
The patent optimizes the concentration ratios of different solvent components to achieve the desired balance. Specifically, it controls the content of cyclic carbonates (EC and PC) within 10-60% by volume, while adjusting chain carbonates and cyclic carboxylic acid esters to achieve optimal low-temperature conductivity (≥0.0084 S/cm at −40°C) while maintaining high flash point properties.
3Reliability
If straight chain or cyclic ethers are used, then ionic conductivity is improved, but flash point decreases and upper temperature storage is limited
Solution Approach 1:
The patent replaces traditional ether-based solvents with a composite system of aprotic solvents including cyclic carbonates, chain carbonates, and cyclic carboxylic acid esters. This composite approach maintains high ionic conductivity while achieving flash points ≥160°C, enabling safe storage and operation at elevated temperatures up to 70°C.
4Reliability
If inorganic electrolytes like LiAlCl4 in thionyl chloride are used, then low-temperature conductivity is improved, but recharging capability is lost
Solution Approach 1:
The patent uses organic aprotic solvents with optimized compositional parameters to achieve conductivity (≥0.0084 S/cm at −40°C) that approaches inorganic electrolytes, while maintaining the recharging capability essential for lithium-ion batteries. The specific ratio of cyclic carbonates, chain carbonates, and cyclic carboxylic acid esters enables both low-temperature performance and rechargeability.
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 system provides high ionic conductivity, stability, and safety by maintaining liquid form down to −71°C, compatibility with metallic lithium, and high anodic voltage limits, reducing the risk of fire and improving power density.
Implementation Method 1
the second aprotic solvent being a fluorinated solvent... which enhances conductivity, flashpoint, and stability
Implementation Method 2
provides high ionic conductivity... allowing operation down to −40°C
Implementation Method 3
maintaining liquid form down to −71°C
Data Source
AI summary
Electrolyte suitable for use in a lithium ion cell or battery. According to one embodiment, the electrolyte includes a fluorinated lithium ion salt and a solvent system that solvates lithium ions and that yields a high dielectric constant, a low viscosity and a high flashpoint. In one embodiment, the solvent system includes a mixture of an aprotic lithium ion solvating solvent and an aprotic fluorinated solvent.