Ionic Liquid Electrolytes for Lithium-Metal Battery Ion Transport
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Solution Overview
Problem
Lithium-metal batteries face issues with poor cycling efficiency, high viscosity of ionic liquids leading to sluggish lithium ion transport, and safety concerns due to thermal instability and uncontrolled solid electrolyte interphase formation, limiting their widespread adoption.
Innovation Solution
A lithium-metal battery electrolyte formulation comprising a core mixture of pyrrolidinium-containing ionic liquids, fluorinated ethers, and specific salts and solvents, optimized by mole fractions, to enhance lithium plating/stripping efficiency and thermal stability, reducing the risk of thermal runaway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ionic liquids are used in lithium-metal batteries, then thermal stability and cathode active material degradation suppression are improved, but viscosity increases leading to sluggish lithium ion transport
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated ether components with specific molecular structures (CF3 groups) and optimizing the ratio of ionic liquid to molecular solvent. This parameter modification reduces viscosity while maintaining thermal stability, thereby improving lithium ion transport rate without sacrificing reliability.
Solution Approach 2:
The patent creates a composite electrolyte system combining ionic liquids (for thermal stability) with fluorinated ether molecular solvents (for low viscosity and high ion mobility). This composite approach allows the electrolyte to simultaneously achieve both thermal stability and fast lithium ion transport by leveraging the complementary properties of different materials.
2Reliability
If ionic liquids are used in lithium-metal batteries, then cathode active material degradation is suppressed, but coulombic efficiency decreases due to poor reductive stability
Solution Approach 1:
The patent modifies the electrolyte composition by adding fluorinated ether components and adjusting the ionic liquid concentration. These parameter changes create a more reductively stable environment at the lithium metal anode interface, improving coulombic efficiency while preserving the cathode protection benefits of ionic liquids.
3Productivity
If lithium metal is repeatedly plated and stripped, then battery capacity is maintained, but porous lithium structure forms reducing cycle life
Solution Approach 1:
The patent changes the electrolyte composition parameters by incorporating fluorinated ethers and optimizing ionic liquid content. These modifications affect the plating morphology of lithium metal, promoting denser and more uniform structures that resist pore formation during repeated cycling, thereby extending cycle life while maintaining capacity.
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 formulation improves lithium-metal battery performance by enhancing coulombic efficiency, reducing impedance, and minimizing thermal runaway risks, thereby increasing safety and cycle life.
Implementation Method 1
a liquid electrolyte. The liquid electrolyte comprises a core mixture and a diluent. The diluent comprises a fluorinated ether
Implementation Method 2
The set of solvents comprises a pyrrolidinium-containing ionic liquid and a molecular solvent
Data Source
AI summary
Described herein are lithium-metal rechargeable electrochemical cells comprising a lithium-metal negative electrode, a positive electrode, and a liquid electrolyte. The liquid electrolyte comprises a core mixture and a diluent. The diluent comprises a fluorinated ether. The core mixture comprises a set of salts and a set of solvents. The set of solvents comprises a pyrrolidinium-containing ionic liquid and a molecular solvent. The molecular solvent is a non-fluorinated ether, for example including but not limited to 1,2-dimethoxyethane. In some examples, the electrolyte further comprises an electrolyte additive, for example including but not limited to tris(trimethylsilyl)phosphate. In some examples, the set of salts comprises one or more imide-containing lithium salts. In some examples, the set of salts comprises lithium bis(fluorosulfonyl)imide and an additional salt and the mole fraction of lithium bis(fluorosulfonyl)imide in the set of salts is 0.5 or greater.