Localized High-Salt Electrolytes with Fluorinated Diluents
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-salt-concentration electrolytes for secondary lithium batteries enhance cycle life but suffer from low conductivity, high viscosity, poor wetting, and increased production costs, along with gas generation issues at high temperatures due to low-boiling solvents like DME.
Innovation Solution
The use of longer-sidechain glyme-based solvents with a fluorinated diluent, such as DEE and TFE, which maintains high salt concentration while reducing viscosity and improving conductivity and wetting, allowing for higher charge-discharge rates and reduced gas generation by forming a stable SEI layer without increasing free solvent molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If high-salt-concentration electrolytes are used, then cycle life is enhanced, but conductivity decreases and viscosity increases
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonates (15-40 vol%) and chain carbonates (5-30 vol%) as diluents. This parameter modification reduces the viscosity and enhances conductivity of the high-salt-concentration electrolyte while maintaining the cycle life benefits, effectively resolving the contradiction between durability and electrical performance
Solution Approach 2:
The patent creates a composite electrolyte system by combining multiple components: lithium salt (1.5-3.0 M), fluorinated cyclic carbonate diluents, chain carbonate diluents, and cyclic carbonate solvents. This composite approach allows the system to simultaneously achieve high cycle life from the concentrated salt and good conductivity from the carbonate diluent mixture
2Duration of action of stationary object
If high-salt-concentration electrolytes are used, then cycle life is enhanced, but wetting of electrodes and separator deteriorates
Solution Approach 1:
The patent modifies the electrolyte composition by adding chain carbonates (5-30 vol%) which have lower viscosity and better wetting properties compared to the concentrated salt solution. This parameter change improves the wetting of electrodes and separator while maintaining the high salt concentration benefits for cycle life
3Stability of the object's composition
If high-salt-concentration electrolytes are used, then SEI stability is improved, but production cost increases
Solution Approach 1:
The patent introduces fluorinated cyclic carbonates and chain carbonates as intermediary diluents that mediate between the concentrated lithium salt and the electrode surfaces. These intermediaries improve the overall system performance and enable the use of optimized salt concentrations, potentially reducing the amount of expensive lithium salt needed while maintaining SEI stability
4Speed
If low-boiling-point DME is used to offset high viscosity, then viscosity decreases, but gas generation increases at high temperatures
Solution Approach 1:
The patent replaces the low-boiling-point DME (which generates gas at high temperatures) with fluorinated cyclic carbonates and chain carbonates that have higher thermal stability. These alternative diluents maintain the necessary fluidity and conductivity without the harmful gas generation issue, effectively substituting a problematic component with a superior one
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 cycle life and charge-discharge rates of lithium-based batteries while reducing gas production and production costs, maintaining high coulombic efficiency and stability at elevated temperatures.
Implementation Method 1
the solvent molecules undergo reduction at the surface of the lithium-metal anode to form a solid-electrolyte interphase (SEI) (passivation) layer
Implementation Method 2
High-salt-concentration electrolytes are known to enhance cycle life in rechargeable, or secondary, batteries having lithium-metal anodes
Data Source
AI summary
Localized high-salt-concentration electrolytes each containing a salt, a glyme as a solvent, and a fluorinated diluent. In some embodiments, the glyme has a chemical formula R1—(O—CH2—CH2)n—O—R2, wherein n=1 to 4 and at least one of R1 and R2 is a hydrocarbon sidechain having at least 2 carbon atoms and wherein the salt is soluble in the glyme. In some embodiments, the fluorinated diluent is selected from the group consisting of a fluorinated glyme and a fluorinated ether. In some embodiments, the salt includes an alkali-metal salt. In some embodiments, the salt includes an alkali-earth-metal salt. The salt may include a perfluorinated sulfonimide salt. Electrochemical devices that include localized high-salt-concentration electrolytes of the present disclosure are also disclosed.