Lithium Battery Electrolyte SEI Layer Stability
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Solution Overview
Problem
Conventional lithium secondary batteries face issues with the stability of the solid electrolyte interface (SEI) layer at high temperatures, leading to increased inner pressure and poor conductivity at low temperatures, which affects their life cycle and charging/discharging performance.
Innovation Solution
A non-aqueous electrolyte solution comprising fluoroethylene carbonate and a pyrimidine-based compound is used, where the fluoroethylene carbonate is in the range of 0.1 to 50 vol% of the total organic solvent, forming a stable SEI layer with high dielectric rate and good lithium-ion conductivity, and the pyrimidine-based compound reacts with the anode to form a dense film inhibiting decomposition reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene carbonate is used in large amount to form SEI layer, then the battery can operate at high voltage, but the SEI layer becomes unstable at high temperature causing continuous decomposition and gas generation
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluoroethylene carbonate (FEC) at 0.1-50 vol% and pyrimidine-based compound at 0.01-10 wt%, replacing part of the conventional ethylene carbonate. This parameter change modifies the SEI layer formation mechanism to create a more stable interface that resists decomposition at high temperatures, thereby reducing gas generation while maintaining high-voltage operation capability.
Solution Approach 2:
The patent creates a composite SEI layer through the synergistic interaction of multiple components: fluoroethylene carbonate provides fluorinated compounds for stable SEI formation, pyrimidine-based compounds contribute nitrogen-containing structures, and conventional carbonates maintain ionic conductivity. This composite approach produces an SEI layer with enhanced thermal stability and reduced decomposition, solving the high-temperature gas generation problem.
2Quantity of substance
If ethylene carbonate is used in large amount, then the battery can provide high energy density, but the battery shows poor conductivity at low temperature due to high freezing point
Solution Approach 1:
The patent modifies the electrolyte composition parameters by adding fluoroethylene carbonate and pyrimidine-based compounds to the conventional ethylene carbonate system. This changes the physical properties of the electrolyte, specifically lowering the freezing point and improving ionic conductivity at low temperatures, while maintaining the high energy density through optimized component ratios.
3Ease of manufacture
If conventional electrolyte composition is used, then the battery can be manufactured simply, but the life cycle is shortened due to SEI layer breakdown at high temperature
Solution Approach 1:
The patent introduces specific compositional parameters (FEC: 0.1-50 vol%, pyrimidine-based compound: 0.01-10 wt%) that optimize SEI layer stability. These parameter changes enhance the battery life cycle by preventing SEI layer breakdown at high temperatures, while the manufacturing process remains relatively simple as it uses conventional electrolyte preparation methods with modified ingredient ratios.
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
This configuration enhances the life characteristics and stability of lithium secondary batteries at both room and high temperatures, maintaining high-rate charging/discharging performance and preventing capacity decrease over multiple cycles.
Implementation Method 1
high reactive lithium reacts with the electrolyte solution and carbon present in the anode active material such as graphite on the surface of the anode active material such as graphite to produce a compound such as Li2CO3, Li2O and LiOH. The produced compound forms a kind of a solid electrolyte interface (SEI) layer on the surface of the anode active material such as graphite.
Implementation Method 2
The SEI layer functions as an ion tunnel, allowing only lithium ions to pass through.
Implementation Method 3
As an effect of such an ion tunnel, the SEI layer prevents the molecule of an organic solvent having large molecular weight, which is included in the electrolyte solution and transferred together with lithium ions, from being inserted between the layers of the anode active material to destroy the structure of the anode.
Implementation Method 4
the pyrimidine-based compound reacts with the anode to form a dense film inhibiting decomposition reactions
Data Source
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AI summary
The present invention provides non-aqueous electrolyte solution for a lithium secondary battery, comprising fluoroethylene carbonate and a pyrimidine-based compound; and a lithium secondary battery using the same.