Diluted Concentrated Battery Electrolytes for Low Volatility and Conductivity
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Solution Overview
Problem
Conventional lithium-ion battery electrolytes face issues with volatility, flammability, increased cost, and reduced conductivity due to high lithium salt concentrations, which hinder their adoption for safe and long-lasting battery cells.
Innovation Solution
The development of diluted concentrated electrolytes, which incorporate a concentrated active salt in a solvent with a diluent to disperse the salt, reducing free solvent molecules and viscosity, thereby minimizing volatility and flammability while maintaining high lithium salt concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lithium salt concentration is increased above conventional 1-2 moles/liter, then volatility and flammability are reduced, but viscosity increases and lithium-ion conductivity decreases
Solution Approach 1:
The electrolyte is segmented into distinct functional regions: concentrated zones with high lithium salt concentration (≥3M) that provide safety by reducing free solvent, and diluent phases that maintain overall流动性 and conductivity. This spatial segmentation allows simultaneous achievement of low volatility and high conductivity.
Solution Approach 2:
The electrolyte uses a composite formulation combining concentrated lithium salt solutions with diluents having complementary properties. The concentrated portions provide safety through reduced volatility, while the diluent portions maintain conductivity, creating a composite electrolyte system that achieves both goals.
2Object-affected harmful factors
If lithium salt concentration is increased to reduce free solvent, then safety is improved, but the amount of lithium salt needed increases cost
Solution Approach 1:
Rather than uniformly concentrating the entire electrolyte volume (which would be expensive), the system segments the electrolyte into concentrated safety-critical zones and diluent zones. This allows safety improvements with minimal lithium salt addition, reducing cost.
Solution Approach 2:
The electrolyte exhibits local quality variations: regions near electrodes have high lithium salt concentration for safety and performance, while other regions use diluents for cost-effectiveness and流动性. This local optimization reduces overall material cost while maintaining safety.
3Object-affected harmful factors
If lithium salt concentration is increased, then volatility is reduced, but internal electrical resistance increases
Solution Approach 1:
The electrolyte system segments high-concentration zones (for low volatility) from diluent zones (for low resistance), allowing the battery to benefit from both low volatility and low internal resistance simultaneously through the distributed architecture.
Solution Approach 2:
The diluent acts as an intermediary that bridges the concentrated lithium salt regions, providing a low-viscosity pathway for ion transport that compensates for the high viscosity in concentrated zones, thereby maintaining rate capability while achieving volatility reduction.
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
This approach enhances the safety, cycle life, and rate capability of lithium-ion battery cells by reducing vapor pressure, internal resistance, and costs associated with high lithium salt concentrations.
Implementation Method 1
a diluent that disperses the concentrate of the active salt and solvent into localized regions of highly concentrated active salt throughout the electrolyte
Implementation Method 2
The high concentrations of active salt in these localized regions integrates almost all the surrounding solvent molecules into coordination complexes, and significantly reduces the amount of free solvent in the electrolyte
Data Source
AI summary
An electrolyte for a lithium-containing battery cell is described. The electrolyte includes a solvent having at least one carbonate ester, and at least one lithium salt having a concentration ranging from 3 mol/liter to 15 mol/liter in the solvent. The electrolyte also includes a diluent that includes an aromatic fluorocarbon. In some embodiments, the solution of the at least one lithium salt and the solvent is a supersaturated solution for at least some operating temperatures of the battery cell. Also described are lithium-containing battery cells that include a positive electrode, a negative electrode, and the electrolyte.