Fluorinated Sulfone Electrolyte for High Voltage Battery Stability
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Solution Overview
Problem
Current lithium ion battery electrolyte solvents, such as linear carbonates, decompose at high cathode potentials above 4.2 V, leading to reduced battery performance, especially at high temperatures and with high voltage cathodes.
Innovation Solution
Development of an electrolyte composition comprising a fluorinated solvent, a fluorinated sulfone, and at least one component selected from borate or oxalate salts, or a fluorinated cyclic carbonate, which forms an electrolyte composition that enhances cycling performance at high temperatures and high voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-aqueous electrolyte solvents (linear carbonates, cyclic carbonates) are used, then the electrolyte composition is simple and commonly available, but the solvents decompose at cathode potentials above 4.2 V, resulting in poor cycling performance at high temperatures and high voltages
Solution Approach 1:
The patent introduces fluorinated solvents and fluorinated sulfones with modified chemical structures that have higher electrochemical stability windows. The fluorination changes the electrical and chemical parameters of the solvent molecules, enabling them to withstand higher cathode potentials (up to 5 V) without decomposition, thus resolving the contradiction between reliability and harmful decomposition effects
Solution Approach 2:
The electrolyte composition combines fluorinated solvents, fluorinated sulfones, and specific salt components (borate salts, oxalate salts) to create a composite electrolyte system. This composite approach leverages the complementary properties of each component to achieve superior cycling performance at high temperatures and voltages while preventing solvent decomposition
2Quantity of substance
If high voltage cathodes (4 V spinel LiMn2O4, 4.7 V LiMn1.5Ni0.5O4) are used to increase energy density, then the battery capacity increases, but the electrolyte solvents decompose more rapidly, reducing battery reliability
Solution Approach 1:
The fluorinated electrolyte components are specifically designed to match the high voltage requirements of advanced cathode materials. The modified solvents maintain their structural integrity at potentials up to 5 V, enabling the use of high-capacity cathodes like LiMn1.5Ni0.5O4 (4.7 V) without suffering from rapid decomposition, thus simultaneously achieving high capacity and reliability
3Power
If high temperature operation is enabled to increase power output, then the battery delivers more power, but the electrolyte decomposition accelerates, reducing operational stability
Solution Approach 1:
The fluorinated sulfones and fluorinated solvents exhibit enhanced thermal stability compared to conventional electrolyte components. The strong C-F bonds and modified molecular structures raise the thermal decomposition temperature of the electrolyte, allowing the battery to operate at elevated temperatures with maintained compositional stability and power output
Data Source
AI summary
Disclosed herein are electrolyte compositions comprising a fluorinated solvent, a fluorinated sulfone, at least one component selected from a borate salt, and/or an oxalate salt, and/or a fluorinated cyclic carbonate, and at least one electrolyte salt. The fluorinated solvent may be a fluorinated acyclic carboxylic acid ester, a fluorinated acyclic carbonate, a fluorinated acyclic ether, or combinations thereof. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries.