Perfluoroalkyl Electrolyte Additives for Lithium Battery SEI Stability
Solution Overview
Problem
Lithium secondary batteries face issues with electrolyte solvent decomposition and the instability of the solid electrolyte interface (SEI) film, leading to performance degradation at high temperatures and inadequate output characteristics, especially at low temperatures, which affects the battery's stability and internal pressure.
Innovation Solution
A non-aqueous electrolyte comprising a lithium salt, a non-aqueous solvent, and specific perfluoroalkyl group-containing additives (Chemical Formulas 2 and 3) is used to enhance the output characteristics of lithium secondary batteries, improving the stability and performance across various temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vinylene carbonate is used as an electrolyte additive to improve high-temperature storage performance and cycle performance, then output performance at low temperature deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte additive by introducing perfluoroalkyl groups with specific chain lengths (C3-C8) and structural configurations (formulas 2 and 3). This chemical parameter modification enables the additive to form an SEI film with improved thermal stability while maintaining low-temperature ionic conductivity, thus resolving the contradiction between high-temperature reliability and low-temperature power output
Solution Approach 2:
The patent creates a composite SEI film structure by combining perfluoroalkyl-containing additives with the base electrolyte system. The perfluoroalkyl groups contribute thermal stability and film-forming capability, while the overall composite structure maintains ion transport properties at low temperatures, achieving both high-temperature reliability and low-temperature power performance
2Stability of the object's composition
If the battery is operated at high temperature, then the SEI film becomes thermally unstable and collapses, but this improves ion transport
Solution Approach 1:
The patent modifies the SEI film composition parameters by incorporating perfluoroalkyl groups (C3-C8) into the electrolyte additive structure. These structural parameters provide enhanced thermal stability to the SEI film, preventing collapse at high operating temperatures while maintaining electrochemical stability and preventing continuous decomposition
Solution Approach 2:
The perfluoroalkyl-containing additive acts as a sacrificial component that forms a stable, long-lasting SEI film during initial cycles. This disposable-like additive consumes itself to create a protective barrier that prevents further electrolyte decomposition and maintains battery performance throughout the service life, especially at high temperatures
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 with perfluoroalkyl group additives significantly improves the output characteristics of lithium secondary batteries, maintaining performance at both high and low temperatures, and reducing internal pressure issues by stabilizing the SEI film.
Implementation Method 1
the SEI film formed on the anode surface owing to reduction of the electrolyte solvent during initial charging of the battery
Implementation Method 2
Electric energy is produced through oxidation-reduction reactions as the lithium ions are intercalated into and deintercalated from the cathode and the anode
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The present disclosure relates to an electrolyte for a lithium secondary battery, comprising a non-aqueous solvent, a lithium salt and an additive having a perfluoroalkyl group. By including the additive having a specific structure in the electrolyte, the output of the lithium secondary battery can be improved greatly.