Lithium Battery Electrolyte Using Cyclic Fluorophosphonate Against Swelling
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Solution Overview
Problem
Lithium secondary batteries face issues with stability and durability at high temperatures due to the volatilization of organic electrolytes and the formation of unstable solid electrolyte interface (SEI) films, leading to battery swelling and performance degradation.
Innovation Solution
Incorporation of a cyclic fluorophosphonate compound in the electrolyte, which interacts with transition metal ions to stabilize the SEI film and prevent battery swelling by forming a stable film on the anode surface, along with additional additives to enhance thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional organic electrolytes are used in lithium secondary batteries, then the battery can operate with standard electrolyte composition, but the electrolyte easily volatilizes and is highly inflammable leading to ignition at high temperatures
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate compounds (fluorinated EC or PC) with specific fluorine substitution patterns. This changes the physical and chemical properties of the electrolyte, resulting in reduced volatility and improved thermal stability while maintaining ionic conductivity.
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate compounds with linear carbonate solvents (DMC, DEC, EMC) and lithium salts. This composite approach leverages the low volatility and high stability of fluorinated compounds while utilizing the good solvating ability of linear carbonates, achieving both thermal stability and electrochemical performance.
2Reliability
If conventional organic electrolytes are used, then the battery structure remains simple, but the SEI film formed on the anode is unstable leading to battery swelling and performance degradation at high temperatures
Solution Approach 1:
The fluorinated cyclic carbonate compounds act as film-forming additives that react preferentially during initial charging cycles to form a stable SEI film on the anode surface before conventional electrolyte decomposition occurs. This preliminary film formation prevents subsequent electrolyte decomposition and gas generation that would cause swelling.
Solution Approach 2:
The introduction of fluorinated cyclic carbonate compounds changes the chemical composition and structure of the SEI film, making it more stable and less prone to decomposition at high temperatures. The fluorine substitution in the cyclic carbonate structure creates a more robust film with better dimensional stability.
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 significantly reduces the thickness increase rate and improves capacity retention and recovery rates at high temperatures, maintaining battery performance and stability.
Implementation Method 1
a cyclic fluorophosphonate compound which interacts with transition metal ions to stabilize the SEI film and prevent battery swelling by forming a stable film on the anode surface
Implementation Method 2
A lithium secondary battery produces electric energy by oxidation and reduction reactions when lithium ions are intercalated into and deintercalated from the cathodes and anodes
Implementation Method 3
lithium ions from a lithium metal oxide which is a cathode at initial charge move to a carbon electrode which is an anode and are intercalated in carbon, in which lithium has strong reactivity so that a surface of a carbon particle, which is an anode active material, and an electrolyte are reacted, while a coating film which is referred to as a solid electrolyte interface (SEI) film is formed on an anode surface
Data Source
AI summary
Provided are an electrolyte for a secondary battery including a lithium salt, a nonaqueous organic solvent, and a cyclic fluorophosphonate compound, and a lithium secondary battery including the same.