Ionic Liquid Electrolytes for Stable Lithium Metal Batteries
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Solution Overview
Problem
Existing lithium rechargeable batteries face challenges in achieving stable electrochemical performance, particularly when using lithium metal anodes, due to issues with electrolyte stability and lithium dendrite formation.
Innovation Solution
Incorporation of short-chain terminally fluorinated glycol ethers and lithium fluorosulfonylimide salts in the electrolyte, optionally with ionic liquids and aprotic gel polymers, to enhance electrolyte stability and improve lithium metal battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes are used with lithium metal anodes, then battery capacity can be achieved, but electrolyte stability deteriorates and lithium dendrite formation occurs
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by incorporating fluorinated carbonates (such as fluoroethylene carbonate and fluoropropylene carbonate) at specific concentrations (1-10% by volume). This parameter modification alters the electrolyte's interaction with lithium metal, preventing dendrite formation while maintaining stability.
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated carbonate additives with conventional carbonate solvents (EC, DMC, DEC). This composite approach leverages the beneficial properties of both components: the fluorinated additives provide protective film formation and dendrite suppression, while the conventional solvents maintain bulk electrolyte conductivity and ion transport.
2Quantity of substance
If lithium metal anodes are used to increase capacity, then battery energy density improves, but cycle life deteriorates due to dendrite formation
Solution Approach 1:
The fluorinated carbonate additives perform preliminary action by forming protective films on the lithium metal surface during initial cycles. This pre-formed protective layer prevents subsequent dendrite growth and electrolyte decomposition, thereby extending the battery's cycle life while maintaining high capacity.
Solution Approach 2:
The fluorinated carbonate additives act as sacrificial components that are consumed during initial cycles to form stable protective films. These small amounts of additive (1-10% by volume) are 'disposed of' in the sense that they decompose to create the protective interface, enabling the long-term stable operation of the lithium metal anode.
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 combination significantly stabilizes lithium metal batteries, reducing dendrite formation and improving cycle life and Coulombic efficiency, thereby enhancing overall battery performance.
Implementation Method 1
an electrolyte comprising a lithium fluorosulfonylimide salt, a terminally fluorinated glycol ether
Implementation Method 2
stabilizes lithium metal batteries, reducing dendrite formation and improving cycle life
Data Source
AI summary
An electrochemical cell includes a cathode of oxygen or a metal oxide; an anode comprising lithium metal; and an electrolyte including a lithium sulfonylimide salt, a terminally fluorinated glycol ether, and an ionic liquid.