Fluorinated Cyclic Carbonate Electrolyte for High-Voltage Lithium-Ion Batteries
Solution Overview
Problem
Lithium-ion batteries face rapid performance fade at high operating potentials due to parasitic reactions between electrolytes and the cathode surface, with conventional electrolyte solvents like ethylene carbonate limiting low-temperature applications and causing severe electrolyte decomposition at high voltages.
Innovation Solution
A non-aqueous electrolyte system incorporating a salt and organosulfamate compounds, such as those described by Formulae (I), (II), and (III), which form effective solid-electrolyte interface (SEI) layers to prevent co-intercalation of electrolyte solvents into graphite electrodes, thereby enhancing battery performance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene carbonate (EC) is used as electrolyte solvent to form SEI layer, then SEI forming properties are improved, but low temperature application is limited due to high melting point
Solution Approach 1:
The patent modifies the chemical structure of cyclic carbonate solvents by introducing fluorine atoms at specific positions (alpha and beta positions relative to the carbonyl group). This structural parameter change reduces the melting point from EC's 36°C to below -49°C (comparable to PC) while preserving the SEI-forming capability, thus resolving the contradiction between SEI formation and low-temperature fluidity.
2Use of energy by moving object
If conventional electrolyte solvents are used at high operating potentials, then energy density is improved, but parasitic reactions with cathode surface cause rapid performance fade
Solution Approach 1:
The patent introduces fluorine substitution at specific positions of the cyclic carbonate molecule. This chemical parameter change increases the electrochemical stability window of the solvent, enabling it to resist parasitic reactions at high potentials (above 4.3V vs Li/Li+) while maintaining high energy density operation, thus resolving the contradiction between energy density and performance stability.
3Temperature
If propylene carbonate (PC) is used as electrolyte solvent to lower melting point, then low temperature fluidity is improved, but co-intercalation with lithium cation into graphite causes poor passivation
Solution Approach 1:
The patent introduces fluorine atoms at specific positions (alpha and beta positions) of the cyclic carbonate structure. This chemical modification changes the solvent's interaction properties with graphite and lithium cations, enabling effective passivation layer formation while maintaining low melting point, thus resolving the contradiction between low-temperature fluidity and passivation quality.
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 use of organosulfamate compounds in the electrolyte significantly inhibits co-intercalation, leading to improved cycling performance, increased discharge capacity, and reduced impedance in lithium-ion batteries, especially at high voltages and low temperatures.
Implementation Method 1
Owing to its outstanding solid-electrolyte interface ('SEI') forming properties, the cyclic carbonate, ethylene carbonate ('EC'), has been an essential electrolyte solvent in conventional electrolyte systems.
Implementation Method 2
it has been found that battery performance fades rapidly at higher and higher operating potentials due, at least in part, to the parasitic reactions between electrolytes and the cathode surface
Data Source
AI summary
A non-aqueous electrolyte comprising a salt, a non-aqueous solvent, and a compound of Formula (I), (II), or (III), where E is —S(O)— or S(O)2—: