Lithium Battery Electrolyte Additives for High-Temperature SEI Protection
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high-temperature performance due to the degradation of the solid electrolyte interphase (SEI) under high-temperature conditions, leading to increased resistance and self-discharge.
Innovation Solution
An electrolyte composition for lithium secondary batteries including a lithium salt, an organic solvent, and specific additives represented by Formulas 1 and 2, which form a robust SEI on both negative and positive electrodes, stabilizing the film structure and suppressing decomposition products that enhance high-temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional electrolyte solutions are used, then the battery can operate at high temperatures, but the SEI decomposes due to activated by-products from salt decomposition, leading to increased resistance and self-discharge
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance that mediates between the electrolyte salt and the SEI layer. This compound preferentially decomposes to form a stable protective film that acts as a barrier, preventing direct contact between activated by-products and the SEI layer, thus protecting the SEI from decomposition while maintaining high-temperature operation
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating fluorinated cyclic carbonate compounds with specific molecular structures (Formula 1 and Formula 2). This parameter change alters the decomposition behavior of the electrolyte, causing the fluorinated compound to decompose first and form a stable protective layer that changes the interface properties between electrolyte and electrode, thereby preventing SEI decomposition at high temperatures
2Productivity
If the SEI is formed on electrodes, then lithium ion transmission is enabled, but the SEI becomes vulnerable to decomposition by activated by-products at high temperatures
Solution Approach 1:
The patent applies beforehand cushioning by having the fluorinated cyclic carbonate compound decompose first during initial cycles to form a stable protective film on the electrode surface. This pre-formed protective layer acts as a cushioning barrier that absorbs and neutralizes the harmful effects of activated by-products before they can reach and decompose the functional SEI layer, thus protecting lithium ion transmission capability
Solution Approach 2:
The patent converts the harmful decomposition reaction into a beneficial protective mechanism. The fluorinated cyclic carbonate compound is designed to decompose preferentially, and this decomposition product forms a stable protective film that benefits the system by shielding the SEI from further decomposition. The harmful by-products are thus converted into a protective barrier that enhances overall battery stability 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 effectively suppresses rapid resistance increases and maintains capacity at high temperatures, enabling the use of silicon-based negative electrodes with large volume changes, thus providing lithium secondary batteries with excellent high-temperature and capacity characteristics.
Implementation Method 1
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 by-product, which is generated by a decomposition reaction of a salt included in the electrolyte solution, is activated and then rather decomposes the SEI
Data Source
AI summary
An electrolyte for a lithium secondary battery and a lithium secondary battery including the same are disclosed herein. In some embodiments, an electrolyte 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.