Non-Aqueous Electrolyte Additive for Stable High-Temperature SEI
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Solution Overview
Problem
Lithium-ion batteries face degradation and thermal runaway due to the instability of the solid electrolyte interphase (SEI) at high temperatures, leading to reduced electrochemical performance and storage stability.
Innovation Solution
A non-aqueous electrolyte solution for lithium secondary batteries is developed, incorporating a compound with a nitrogen and fluorine element, which forms a robust passivation film on the electrodes, enhancing high-temperature storage stability and capacity characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used, then the battery can operate at normal temperatures, but the SEI becomes unstable at high temperatures causing degradation and thermal runaway
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by introducing a fluorinated cyclic carbonate compound with specific molecular structure (Formula 1) where R is alkylene with 1-4 carbon atoms and R1 is fluorinated alkyl with 1-5 carbon atoms. This parameter change in the electrolyte composition enables formation of a thermally stable SEI layer that prevents degradation at high temperatures while maintaining normal battery operation
Solution Approach 2:
The patent creates a composite SEI layer on the electrode surface through the fluorinated additive, combining the original SEI components with fluorinated decomposition products. This composite structure provides enhanced thermal stability and robust passivation, preventing both SEI degradation and thermal runaway conditions while maintaining ionic conductivity
2Reliability
If the SEI is damaged at high temperatures, then additional electrolyte decomposition occurs, but this consumes lithium and electrons causing performance degradation
Solution Approach 1:
The fluorinated cyclic carbonate compound acts as a preliminary protective agent that pre-forms a stable SEI layer before high-temperature conditions occur. This preliminary action prevents the sequence of SEI damage followed by electrolyte decomposition, thereby preventing consumption of lithium and electrons that would lead to performance degradation
3Reliability
If a robust passivation film is formed using the fluorinated compound, then high-temperature storage stability improves, but the internal structure becomes more complex
Solution Approach 1:
The fluorinated cyclic carbonate compound concentrates its protective effect locally at the electrode surface where the SEI layer forms. The additive maintains simple bulk electrolyte composition while creating a complex, stable passivation film only where needed at the electrode interface, thus improving high-temperature stability without significantly increasing overall device complexity
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 effectively prevents degradation of the SEI at high temperatures, improving the battery's high-temperature storage stability, cycle performance, and reducing resistance, thereby extending the battery's lifespan and maintaining capacity retention.
Implementation Method 1
reductive decomposition of the electrolyte precedes, a passivation layer which is a reductive decomposition product of the electrolyte, that is, a solid electrolyte interphase (SEI) is formed on a surface of the electrode
Implementation Method 2
it has a characteristic that allows lithium ions to be transmitted but inhibits electron transmission
Implementation Method 3
a compound represented by Formula 1... which includes at least one nitrogen element and at least one fluorine element in its molecular structure, as an additive, a robust passivation film may be formed on a surface of a positive electrode or a negative electrode
Data Source
AI summary
The present invention provides a non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same. Specifically, since the non-aqueous electrolyte solution forms a robust solid electrolyte interphase (SEI) by including a lithium salt, an organic solvent, and a compound represented by Formula 1, the non-aqueous electrolyte solution for a lithium secondary battery may improve battery performance,wherein, in Formula 1,R and R1 are described herein.