Sulfolane Electrolyte Composition for High-Voltage Lithium Batteries
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Solution Overview
Problem
Current lithium-ion batteries face limitations in energy density and safety due to electrolyte stability issues, particularly at higher operating voltages, leading to poor cyclability and flammability, which restricts their application in high-end portable devices.
Innovation Solution
A sulfolane-based electrolyte composition comprising lithium bis(trifluoromethansolfonyl)imide (LiTFSI), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), and fluoroethylene carbonate (FEC) is developed, with specific molar ratios and volume percentages to enhance stability and safety, allowing for higher energy density and extended cycle life at voltages above 4.4V.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional electrolyte compositions are used, then the battery can operate at standard voltages (4.2V-4.4V), but the energy density is limited and the battery becomes flammable
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated carbonates (FEC, DFEC) and cyclic sulfones (SL, GVL) in specific ratios, replacing conventional carbonate mixtures. This parameter change enables operation at higher voltages (4.4V-4.6V) while maintaining safety, thus increasing energy density without flammability
Solution Approach 2:
The patent creates a composite electrolyte system combining fluorinated carbonate esters with cyclic sulfone compounds in specific molar ratios (0.5:1 to 2:1). This composite approach synergistically combines the high voltage stability of fluorinated compounds with the safety and ionic conductivity of cyclic sulfones, achieving both high energy density and fire safety
2Use of energy by moving object
If the operating voltage is increased above 4.4V to improve energy density, then the energy density increases, but the electrolyte stability deteriorates leading to poor cyclability
Solution Approach 1:
The patent optimizes the voltage parameter range to 4.4V-4.6V and adjusts the electrolyte composition parameters (fluorinated carbonate to cyclic sulfone ratio) to match this voltage window. This coordinated parameter change enables high energy density operation while maintaining electrolyte stability and achieving excellent cyclability (93% capacity retention after 500 cycles)
3Use of energy by moving object
If lithium metal anode is used to increase energy density, then the energy density increases, but the coulombic efficiency decreases leading to poor cyclability
Solution Approach 1:
The patent introduces a specially formulated electrolyte composition as an intermediary between the lithium metal anode and the rest of the battery system. The fluorinated carbonates and cyclic sulfones in this electrolyte form a stable protective interface that mediates the interaction between lithium metal and the electrolyte, enabling high coulombic efficiency (97-98%) and excellent cyclability while maintaining high energy density
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 composition achieves a coulombic efficiency of at least 93%, significantly improving the energy density and cycle life of lithium-ion batteries while ensuring safety by maintaining stability and preventing flammability, enabling operation at higher voltages.
Implementation Method 1
The electrolyte should conduct lithium ions, acting as a carrier between the cathode and the anode when a battery passes an electric current through an external circuit
Implementation Method 2
Electrolyte solvents in current use decompose on initial charging and form a solid interphase layer, which is electrically insulating, yet provides sufficient ionic conductivity
Data Source
AI summary
The present invention relates to an electrolyte composition suitable for lithium secondary batteries, comprising a specific lithium salt, preferably lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a fluorinated ether, preferably 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), a cyclic sulfone, preferably sulfolane (SL), and a fluorinated carbonate, preferably fluoroethylene carbonate (FEC), in an amount (x) of 0<x<=15 voL %, wherein the cyclic sulfone/lithium salt is comprised in a molar ratio (y) of 1.0<=y<=5.0 and the fluorinated ether/lithium salt is comprised in a molar ratio (z) of 1.0<=z<=5.0. The electrolyte according to the invention results in improved electrochemical properties.