Li-Ion Electrolyte Composition for Stable CEI at High Voltage
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Solution Overview
Problem
Lithium-ion batteries experience damage to the electrochemical interface (CEI) film on the positive electrode plate, leading to increased alternating current impedance and intermittent cycling performance issues, particularly at high temperatures.
Innovation Solution
An electrolyte composition comprising lithium bis(fluorosulfonyl)imide, a sulfur-containing compound, and propyl propionate, with specific mass ratios, forms a stable and uniform CEI film on the positive electrode plate, suppressing acidic gas generation and enhancing structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes are used in lithium-ion batteries, then the batteries can operate, but the CEI film on the positive electrode plate is damaged at high temperatures, leading to increased alternating current impedance and poor cycling performance
Solution Approach 1:
The sulfur-containing compound acts as an intermediary substance that mediates between the electrolyte and the positive electrode plate. It优先 reacts with the electrode to form a protective interface layer, preventing direct contact and harmful reactions between the electrolyte components and the electrode, thereby protecting the CEI film from damage at high temperatures
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by introducing specific sulfur-containing compounds (such as sultone derivatives) with controlled concentrations (0.1-5 wt%). This parameter change modifies the interfacial chemistry, enabling the formation of a stable CEI film that resists high-temperature degradation
2Reliability
If the electrolyte composition is optimized to protect the CEI film, then the alternating current impedance is reduced, but the electrolyte composition becomes more complex
Solution Approach 1:
The patent combines multiple functions into a single sulfur-containing compound additive: it serves as both a CEI film protective agent and a cycling performance enhancer. By merging these functions into one compound class (sultone derivatives), the electrolyte formulation remains relatively simple while achieving multiple performance improvements
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 composition improves drop resistance and intermittent cycling performance by reducing alternating current impedance and preventing corrosion of the positive electrode active material, ensuring better chemical and structural stability.
Implementation Method 1
during the charge-discharge process of the electrochemical apparatus, especially in the initial few charge-discharge processes, the bis(fluorosulfonyl)imide anion (FSO3) reacts with the sulfur-oxygen double bond to form a stable and uniform electrochemical interface (CEI) film structure
Implementation Method 2
the bis(fluorosulfonyl)imide anion (FSO3) reacts with the sulfur-oxygen double bond to form a stable and uniform electrochemical interface (CEI) film structure, which can suppress the generation of acidic gases
Data Source
AI summary
An electrolyte includes lithium bis(fluorosulfonyl)imide, a sulfur-containing compound, and propyl propionate. Based on a mass of the electrolyte, a mass percentage of lithium bis(fluorosulfonyl)imide is A%, a mass percentage of the sulfur-containing compound is B%, and a mass percentage of propyl propionate is D%, where 0.3 ≤ B/A ≤ 4, and 30 ≤ D ≤ 40. With the above configuration, the risk of increased alternating current impedance of the electrochemical apparatus under high voltage can be reduced, and the drop resistance and intermittent cycling performance of the electrochemical apparatus can be improved.