Non-Aqueous Electrolyte Composition for Heat-Stable SEI Protection
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Solution Overview
Problem
The thermal decomposition of lithium salts in non-aqueous electrolytes used in lithium secondary batteries generates Lewis acids, leading to the degradation of the solid electrolyte interface (SEI) layer and increased resistance, which affects the battery's lifespan and storage performance.
Innovation Solution
A non-aqueous electrolyte composition comprising a lithium salt, cyclic carbonate compounds, and specific organic solvents, along with optional additives, is developed to enhance stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as the lithium salt in the electrolyte, then the battery can operate with good performance under normal conditions, but when exposed to high temperatures, thermal decomposition generates Lewis acids (HF and PF5) that destroy the SEI layer and cause battery degradation
Solution Approach 1:
The patent introduces a sulfonamide compound as an intermediary substance in the electrolyte that acts as a precursor to generate protective species in situ. This intermediary compound reacts with the Lewis acids (HF and PF5) generated from LiPF6 decomposition, converting harmful substances into beneficial protective layers that stabilize the SEI and prevent further degradation, thus resolving the contradiction between maintaining battery performance and preventing thermal decomposition damage
Solution Approach 2:
The patent modifies the electrolyte composition by adding specific amounts of sulfonamide compounds (0.1-10 wt% relative to lithium salt) and adjusting the ratio of cyclic carbonate to chain carbonate solvents. These parameter changes alter the chemical environment in the electrolyte, enabling the sulfonamide to effectively scavenge Lewis acids while maintaining ionic conductivity, thereby improving thermal stability without sacrificing battery performance
2Reliability
If the electrolyte uses conventional carbonate-based organic solvents, then the battery achieves good ionic conductivity, but the SEI layer becomes vulnerable to decomposition at elevated temperatures leading to increased resistance and reduced lifespan
Solution Approach 1:
The sulfonamide compound is pre-added to the electrolyte formulation before battery assembly. Upon initial charging cycles or upon exposure to elevated temperatures, the sulfonamide proactively reacts with potential Lewis acids and participates in SEI formation, creating a pre-stabilized protective layer before thermal degradation can occur. This preliminary action prevents the vulnerability of the SEI layer to decomposition, extending battery lifespan while maintaining ionic conductivity
Solution Approach 2:
The patent creates a composite electrolyte system combining conventional carbonate solvents (for ionic conductivity) with sulfonamide compounds (for thermal stability). This composite formulation integrates the beneficial properties of both components: the carbonate solvents ensure good ion transport, while the sulfonamide provides thermal protection by scavenging Lewis acids and stabilizing the SEI layer, thus resolving the contradiction between conductivity and lifespan
3Quantity of substance
If the electrolyte contains lithium salts susceptible to thermal decomposition, then the battery can deliver high capacity under normal conditions, but storage performance deteriorates due to SEI layer destruction and gas generation
Solution Approach 1:
The patent converts the harmful thermal decomposition reaction of lithium salts into a beneficial process by introducing sulfonamide compounds that selectively react with the generated Lewis acids. The decomposition products (HF and PF5) that would normally destroy the SEI layer are instead transformed into protective species through reaction with sulfonamide, forming stable compounds and regenerating protective SEI components. This converts the harmful decomposition into a beneficial self-healing mechanism, improving storage performance while maintaining capacity
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 improves the stability and safety of lithium secondary batteries by reducing thermal decomposition and maintaining the integrity of the SEI layer, thereby extending the battery's lifespan and enhancing storage performance.
Implementation Method 1
the compound according to Chemical Formula 1... reacts with Lewis acids generated from lithium salt decomposition
Implementation Method 2
an electrolyte that serves as a medium for transferring lithium ions
Data Source
AI summary
Disclosed is a non-aqueous electrolyte including a lithium salt and an organic solvent. The organic solvent includes a cyclic carbonate and a compound represented by Chemical Formula 1:R1 is a fluorine atom, an alkyl group having 1 to 10 carbon atoms substituted with one or more fluorines, or an alkoxy group having 1 to 10 carbon atoms substituted with one or more fluorines; and R2 and R3 are independently hydrogen, alkyl groups with 1 to 10 carbon atoms, or aryl groups with 6 to 20 carbon atoms.