Sulfolane Li Secondary Battery Electrolyte for 4.5V Stability
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Solution Overview
Problem
Current lithium-ion battery electrolytes limit the operating voltage of portable electronic devices to around 4.4V, leading to a plateau in energy density and safety issues due to flammability, while also restricting cycle life and coulombic efficiency.
Innovation Solution
A sulfolane-based electrolyte composition with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 39.0-47.5 vol% and fluoroethylene carbonate (FEC) in 1.0-15.0 vol%, with a molar ratio of sulfolane to LiTFSI ranging from 2.0 to 3.5, enhancing stability and safety for higher voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solvents (EC, DMC, PC) with LiPF6 are used, then ionic conductivity is achieved, but operating voltage is limited to 4.4V and flammability safety issues occur
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing conventional carbonate solvents with sulfolane as the main solvent and using LiTFSI as the lithium salt. This parameter change fundamentally alters the electrochemical stability window and safety characteristics, enabling operation at 4.4-4.5V while eliminating flammability issues.
Solution Approach 2:
The patent creates a composite electrolyte system combining sulfolane solvent with LiTFSI salt in specific ratios (39.0-47.5 vol%). This composite material approach leverages the high electrochemical stability of sulfolane and the low solubility characteristics of LiTFSI to achieve both high voltage operation and safety.
2Use of energy by moving object
If operating voltage is increased beyond 4.4V for higher energy density, then energy density improves, but electrolyte stability deteriorates and safety issues arise
Solution Approach 1:
The patent changes the electrochemical parameters of the electrolyte system by introducing sulfolane, which has a wide electrochemical stability window. This allows the battery to operate at higher voltages (4.4-4.5V) without electrolyte decomposition, thereby increasing energy density while maintaining stability.
3Reliability
If LiTFSI concentration is increased to improve voltage stability, then operating voltage stability improves, but LiTFSI solubility becomes limiting
Solution Approach 1:
The patent accepts the limitation of LiTFSI solubility and uses it strategically by maintaining a specific concentration range (39.0-47.5 vol%) where the salt provides sufficient voltage stability without exceeding solubility limits. The system is designed to operate optimally within this constrained composition range.
4Quantity of substance
If conventional electrolytes are used for high capacity batteries, then capacity is achieved, but cycle life and coulombic efficiency are restricted
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte to sulfolane-based composition, which provides superior electrochemical stability over repeated cycling. This results in high coulombic efficiency (≥93%) and extended cycle life while maintaining high capacity, as the stable electrolyte composition prevents degradation reactions during charge-discharge cycles.
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 solution achieves high coulombic efficiency of at least 93%, supports higher voltage ranges up to 4.5V, and improves cycle life and energy density, while maintaining safety and stability, thus overcoming the limitations of conventional electrolytes.
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. This interphase prevents further decomposition of the electrolyte in subsequent charge/discharge cycles
Data Source
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AI summary
The present invention relates to a sulfolane-based electrolyte composition suitable for Lithium secondary batteries, comprising lithium bis(trifluoromethansolfonyl)imide (LiTFSI) in an amount (x) of 39.0 vol% ≤ x ≤ 47.5 vol%, fluoroethylene carbonate (FEC) in an amount (y) of 0 < y ≤ 15 vol%, equivalent to an amount of 0 < y ≤ 14.0 wt.%, relative to the total volume, respectively weight, of the electrolyte composition, and sulfolane, wherein SL/LiTFSI is comprised in a molar ratio (z) of 2 ≤ z ≤ 3.5 as well as its application in a Lithium secondary battery cell.