Lithium Battery Electrolyte Composition for High-Temperature SEI Passivation
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Solution Overview
Problem
Lithium secondary batteries face performance degradation and self-discharge issues at high temperatures due to side reactions caused by decomposition of lithium salts, leading to increased resistance and reduced capacity, particularly due to inadequate passivation of the solid electrolyte interphase (SEI).
Innovation Solution
An electrolyte composition including a specific additive with a compound represented by Formula 1 and an oligomer with an acrylate group, combined with a lithium salt and organic solvent, is used to suppress side reactions and enhance high-temperature performance by forming a passive layer on the electrode interfaces, thereby maintaining the stability of the SEI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional electrolyte solutions are used in lithium secondary batteries, then the batteries can operate at high voltage and high temperature, but the electrolyte solution deteriorates due to decomposition of lithium salts, causing side reactions, increased resistance, and decreased capacity
Solution Approach 1:
The patent introduces a specific additive compound (Formula 1) as an intermediary substance that mediates between the lithium salt and the electrode surfaces. This additive preferentially reacts with decomposition products like HF and PF5 to form a protective film, preventing these harmful substances from attacking the SEI and electrolyte solution, thus maintaining stability at high temperatures
Solution Approach 2:
The patent converts the harmful decomposition products of lithium salts (such as HF and PF5) into beneficial protective components. By designing the additive to react with these decomposition products and form stable fluorinated compounds, the harmful substances are transformed into useful film-forming agents that enhance SEI stability and protect the electrolyte solution from further decomposition
2Power
If the operating voltage is increased to improve energy density, then the battery capacity increases, but the electrolyte solution decomposes more readily, leading to performance degradation
Solution Approach 1:
The patent applies preliminary anti-action by having the additive compound react with potential decomposition products before they can cause harm. The additive is designed to preemptively scavenge HF and PF5 and form a stable protective film on the SEI, preventing subsequent decomposition reactions that would otherwise be triggered by high voltage operation
Solution Approach 2:
The patent creates a composite protective layer on the SEI surface consisting of the original SEI structure combined with fluorinated compounds derived from the additive. This composite film has enhanced stability and resistance to high voltage decomposition, allowing the battery to operate at higher voltages without electrolyte degradation
3Speed
If the SEI passivation ability is insufficient, then lithium ion transmission is maintained, but additional electrolyte solution decomposition occurs, causing self-discharge and potential reduction
Solution Approach 1:
The patent changes the chemical composition parameters of the SEI by introducing fluorinated compounds through the additive. This modifies the SEI's physical and chemical properties, enhancing its passivation ability while maintaining lithium ion conductivity. The fluorinated film creates a more stable interface that prevents electron transfer reactions responsible for self-discharge
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 proposed electrolyte composition significantly minimizes battery performance degradation and internal resistance increase, even at elevated temperatures, while maintaining ionic conductivity and improving high-temperature safety by effectively scavenging decomposition products and forming a stable film on the electrodes.
Implementation Method 1
forming a passive layer on the electrode interfaces, thereby maintaining the stability of the SEI
Implementation Method 2
scavenging decomposition products and forming a stable film on the electrodes
Implementation Method 3
an electrolyte solution that becomes a medium for transferring lithium ions
Data Source
AI summary
An electrolyte for a lithium secondary battery and a lithium second battery including the same are disclosed herein. In some embodiments, an electrolyte includes an additive containing a compound represented by Formula 1, an oligomer containing a unit represented by Formula 2 and having an acrylate group at an end thereof, a lithium salt, and an organic solvent.