Organosilicon Electrolyte for High-Temperature Li-Ion Stability
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Solution Overview
Problem
Current Li-ion battery electrolytes are unstable above 60°C and at charge voltages above 4.3 volts, leading to rapid degradation of electrode materials and battery performance, and their flashpoints are too low, posing safety risks and limiting the development of advanced Li-ion batteries for various applications.
Innovation Solution
Development of electrolyte compositions comprising organosilicon compounds and imide-containing compounds, which provide increased thermostability, higher flash points, and improved voltage stability, allowing for the use of high-temperature and high-voltage applications, and are compatible with existing Li-ion battery systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LiPF6 electrolytes are used in Li-ion batteries, then good electrochemical performance is achieved at normal conditions, but thermal stability and voltage stability deteriorate above 60°C and 4.3V
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing LiPF6 with LiTFSI and adding organosilicon compounds (cyclic siloxanes and chain siloxanes) in specific ratios. This parameter change enables the electrolyte to maintain stability at temperatures above 60°C and voltages above 4.3V while preserving electrochemical performance. The specific parameter range includes 1-10 wt% cyclic siloxane and 90-95 wt% chain siloxane, which optimizes both thermal and electrochemical properties.
Solution Approach 2:
The patent creates a composite electrolyte system by combining multiple components: LiTFSI salt, cyclic siloxane (e.g., 1,3-propanesultone), and chain siloxane (e.g., polydimethylsiloxane). This composite material approach allows the electrolyte to exhibit synergistic properties where the cyclic siloxane provides thermal stability and film formation, while the chain siloxane ensures good ionic conductivity and electrochemical performance, resolving the contradiction between stability and performance.
2Use of energy by moving object
If conventional carbonate electrolytes are used, then good ionic conductivity is achieved, but flashpoint is too low causing safety risks
Solution Approach 1:
The patent changes the physical and chemical parameters of the electrolyte by introducing organosilicon compounds with high thermal stability and high flashpoints. The chain siloxane component (polydimethylsiloxane) specifically provides high flashpoint properties while maintaining ionic conductivity through its molecular structure and flexibility. This parameter change shifts the flashpoint to much higher temperatures while preserving energy transfer efficiency.
Solution Approach 2:
The cyclic siloxane (1,3-propanesultone) acts as an intermediary substance that forms protective films on electrode surfaces. This film acts as a mediator that prevents direct contact between the electrolyte and electrode, reducing harmful reactions and improving safety. The intermediary layer maintains good ionic conductivity while providing thermal and electrochemical stability, effectively decoupling the conductivity requirement from the safety risk.
3Quantity of substance
If Li-ion batteries operate above 60°C and 4.3V, then higher energy density is achieved, but rapid degradation of electrode materials occurs
Solution Approach 1:
The patent applies preliminary action by having the cyclic siloxane component (1,3-propanesultone) react first to form stable protective films on the electrode surfaces before the battery operates at high temperatures or voltages. This pre-formed protective layer prevents subsequent degradation of electrode materials during high-energy-density operation. The preliminary film formation occurs during initial cycles or conditioning, preparing the electrode surface for harsh operating conditions.
Solution Approach 2:
The organosilicon-containing electrolyte provides beforehand cushioning by creating a stable interfacial layer that cushions and protects electrode materials from thermal and electrochemical stress during high-temperature and high-voltage operation. This protective cushioning effect prevents rapid degradation and extends battery life, allowing the battery to safely operate at higher energy densities without sacrificing durability.
Data Source
AI summary
Described are electrolyte compositions and electrochemical devices containing the electrolyte compositions. The compositions include an organosilicon compound, an imide salt and optionally LiPF6. The electrolytes provide improved high-temperature performance and stability and will operate at temperatures as high as 250° C.