LiFSI Fluorinated Ester Electrolyte for High-Voltage Li-Ion Cycling
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Solution Overview
Problem
Lithium ion batteries face challenges with the decomposition of commonly used non-aqueous electrolyte solvents at high cathode potentials, leading to reduced battery performance, and existing formulations do not adequately address cycle performance at low and high temperatures and storage performance at high temperatures.
Innovation Solution
A fluorinated solvent-based electrolyte composition comprising lithium bis(fluorosulfonyl)imide and at least one electrolyte salt, specifically using acyclic carboxylic acid esters as the fluorinated solvent, which enhances the stability and performance of lithium ion batteries across various temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If commonly used non-aqueous electrolyte solvents are used, then the electrolyte can dissolve electrolyte salts and additives, but the solvents decompose at cathode potentials above 4.35 V, resulting in loss of battery performance
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte solvent by introducing fluorinated cyclic carbonate compounds (FEC, FDMC, FDMS) with specific fluorine substitution patterns. This chemical parameter change increases the oxidation potential and stability of the solvent, allowing it to resist decomposition at high cathode potentials above 4.35 V while maintaining dissolving capability for electrolyte salts and additives.
Solution Approach 2:
The patent creates a composite electrolyte solvent system by combining fluorinated cyclic carbonate compounds with other carbonate solvents (cyclic and linear). This composite formulation synergistically combines the high stability and oxidation resistance of fluorinated compounds with the good dissolving properties and ionic conductivity of conventional carbonates, achieving both reliability and compositional stability.
2Stability of the object's composition
If electrolyte formulations are optimized for high temperature stability, then storage performance improves, but cycle performance at low and high temperatures deteriorates
Solution Approach 1:
The patent applies local quality by using fluorinated cyclic carbonate compounds that specifically stabilize the electrolyte composition at high temperatures through their thermal stability and resistance to decomposition. These compounds locally address high-temperature storage stability without compromising low-temperature ionic conductivity and cycle performance, as the fluorinated structure provides targeted thermal protection while maintaining overall electrolyte functionality across temperature ranges.
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 improves cycle performance at low and high temperatures and storage performance at high temperatures, as demonstrated by increased capacity retention and reduced swelling in cycling and storage tests.
Implementation Method 1
The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries
Implementation Method 2
The solvent must dissolve the electrolyte salt as well as the additives
Data Source
AI summary
Disclosed are electrolyte compositions comprising a fluorinated acyclic carboxylic acid ester, lithium bis(fluorosulfonyl)imide (also called LiFSI); and at least one electrolyte salt. The electrolyte compositions are useful in electrochemical cells, such as lithium-ion batteries.