Lithium Battery Electrolyte Composition for High-Temperature SEI Stability
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Solution Overview
Problem
Lithium secondary batteries face issues with high-temperature performance due to decomposition of the electrolyte solution, leading to increased resistance and reduced capacity, particularly when using silicon-based negative electrodes with large volume changes.
Innovation Solution
An electrolyte composition for lithium secondary batteries comprising a lithium salt, organic solvent, and specific additives that form a robust solid electrolyte interphase (SEI) to stabilize the electrodes, including compounds represented by Formulas 1 and 2, along with additional additives to enhance film formation on both positive and negative electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used, then the battery can operate normally, but under high-temperature conditions the electrolyte decomposes causing increased resistance and reduced capacity
Solution Approach 1:
The patent applies preliminary action by introducing additives (compounds of Formulae 1 and 2) that proactively form a protective SEI film on the electrode surfaces before high-temperature decomposition occurs. This pre-formed robust SEI layer prevents subsequent electrolyte decomposition and maintains stable battery performance under high-temperature conditions.
Solution Approach 2:
The patent uses additives as intermediary substances that mediate between the electrolyte and electrode surfaces. These additives form a protective SEI film that acts as an intermediary layer, preventing direct contact and harmful reactions between the electrolyte and electrodes under high-temperature conditions, thus resolving the stability issue.
2Quantity of substance
If silicon-based negative electrodes are used to increase capacity, then energy density improves, but volume changes during cycling cause SEI damage and electrolyte decomposition
Solution Approach 1:
The patent applies beforehand cushioning by having the additives form a pre-cushioned protective SEI film on the silicon-based negative electrode surface before volume expansion occurs during cycling. This pre-formed protective layer cushions and protects the electrode from mechanical damage during volume changes, maintaining cycle stability.
Solution Approach 2:
The patent uses composite materials by creating a composite SEI structure consisting of the robust SEI film formed by the additives (Formulae 1 and 2) on top of the silicon-based negative electrode. This composite structure combines the high capacity of silicon with the stability of the protective SEI layer, resolving the contradiction between capacity and cycle stability.
3Stability of the object's composition
If the SEI film is made more robust to prevent decomposition, then high-temperature stability improves, but the formation process becomes more complex
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the electrolyte through the addition of specific compounds (Formulae 1 and 2). These parameter changes in electrolyte composition enable the formation of a more robust SEI film that provides high-temperature stability without requiring complex device structural changes.
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 composition effectively suppresses resistance increases and maintains capacity under high-temperature conditions, enabling the use of silicon-based negative electrodes and improving overall battery performance.
Implementation Method 1
The electrolyte solution causes a reduction decomposition reaction on an interface of the negative electrode during an activation process of the battery, and a reduced and decomposed product forms a solid electrolyte interphase (SEI) that transmits lithium ions, but suppresses additional decomposition of the electrolyte solution.
Implementation Method 2
a lithium salt; an organic solvent; and an additive
Data Source
AI summary
The present invention relates to an electrolyte for a lithium secondary battery, which includes a lithium salt, an organic solvent, and an additive, wherein the additive includes a compound represented by Formula 1 and a compound represented by Formula 2, and a lithium secondary battery including the electrolyte for a lithium secondary battery.