Polymer Electrolyte Additives for Lithium Battery Thermal Stability
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Solution Overview
Problem
Rechargeable lithium batteries face issues with cycle-life stability, particularly at high temperatures and under high rate conditions, due to the decomposition of the organic SEI film leading to internal pressure increases and structural distortion.
Innovation Solution
A polymer electrolyte comprising a lithium salt, a non-aqueous organic solvent, and an additive that includes a polyester polyol-based monomer, alkyl acrylate, and a phosphate-based compound, which enhances thermal stability and cross-linking density, suppressing film decomposition and maintaining battery integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an organic electrolyte is used in a rechargeable lithium battery, then high energy density and high discharge voltage are achieved, but the organic SEI film decomposes at high temperatures causing internal pressure increase and battery swelling
Solution Approach 1:
The patent applies preliminary action by introducing a specific additive (vinylene carbonate in combination with fluoroethylene carbonate) before the high-temperature decomposition occurs. This additive pre-forms a stable protective film on the electrode surface during initial cycles, creating a barrier that prevents subsequent decomposition of the organic SEI film at high temperatures, thus preventing internal pressure buildup and maintaining reliability.
Solution Approach 2:
The patent uses an intermediary substance (the additive mixture of vinylene carbonate and fluoroethylene carbonate) that mediates between the organic electrolyte and the electrode. This intermediary forms a stable interfacial layer that allows ion transport while blocking harmful decomposition reactions, enabling the system to maintain both high energy density and thermal stability.
2Temperature
If the battery is kept at high temperature after full charge, then thermal energy increases causing continuous SEI film decomposition, but this leads to increased internal pressure and battery distortion
Solution Approach 1:
The patent applies beforehand cushioning by incorporating an additive system that proactively cushions against thermal decomposition. The vinylene carbonate and fluoroethylene carbonate additives create a thermally stable protective layer in advance, which cushions the electrode interface against the damaging effects of high-temperature exposure, preventing gas generation and internal pressure increase that would cause distortion.
3Reliability
If lithium ions react with carbon negative electrode during initial charge, then SEI film is formed preventing further reactions, but this reaction generates gases causing battery swelling
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the electrolyte system. By adding vinylene carbonate and fluoroethylene carbonate to the organic electrolyte mixture, the chemical parameters of the SEI film formation process are changed, resulting in a passivation layer that forms with minimal gas generation while maintaining its protective function.
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 solution provides improved cycle-life characteristics at room and high temperatures, along with high rate performance, by stabilizing the electrolyte and preventing thickness expansion, thus enhancing the reliability and durability of the lithium battery.
Implementation Method 1
carbon of a negative electrode reacts with an electrolyte at initial charge to form a passivation layer such as a SEI film on a surface of the negative electrode
Implementation Method 2
the organic SEI film gradually decomposes based on the electrochemical energy and thermal energy that increases as time passes
Data Source
AI summary
An electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same, and the electrolyte includes a lithium salt, a non-aqueous organic solvent, and an additive,wherein the additive includesa polyester polyol-based monomer represented by the following Chemical Formula 1;C1 to C10 alkyl acrylate; anda phosphate-based compound selected from triallyl phosphate represented by the following Chemical Formula 10, triacryl phosphate represented by the following Chemical Formula 11, or a combination thereof:In Chemical Formula 1, each substituent is the same as described in the detailed description.