Lithium Battery Electrolyte Composition for Stable Interface Films
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Solution Overview
Problem
Existing secondary batteries experience a significant decrease in storage performance and cycling performance, and an increase in DC internal resistance after multiple cycles.
Innovation Solution
An electrolyte solution for lithium secondary batteries containing sulfate and fluorosulfonate ions, with specific molar ratios and concentrations, forms a dense composite film at the positive and negative electrode interfaces, enhancing thermal and mechanical stability and ionic conductivity, thereby reducing DC internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used in secondary batteries, then the batteries can operate initially, but after multiple cycles the storage performance and cycling performance significantly decrease and DC internal resistance significantly increases
Solution Approach 1:
The patent uses a composite electrolyte system containing both sulfate ions (SO4^2-) and fluorosulfonate ions (FSO3^-) in specific molar ratios (8-223:1). This composite ionic composition creates a synergistic effect where sulfate provides structural stability and fluorosulfonate enhances ionic conductivity, resulting in a stable solid electrolyte interface (SEI) film that maintains battery performance over extended cycling periods
Solution Approach 2:
The patent optimizes specific parameters including the molar ratio of sulfate to fluorosulfonate ions (8-223:1), molar concentration of sulfate (0.08-0.2 mol/L), and molar concentration of fluorosulfonate ions (0.0009-0.009 mol/L). These parameter optimizations enable the formation of a balanced interface film that simultaneously provides mechanical stability and ionic conductivity, preventing performance degradation over time
2Stability of the object's composition
If the interface film is made denser to improve stability, then thermal and mechanical stability improve, but ionic conductivity may decrease
Solution Approach 1:
The dual-ion composition (sulfate and fluorosulfonate) creates a composite interface film with heterogeneous structure. Sulfate ions form dense, stable regions providing mechanical and thermal stability, while fluorosulfonate ions create more conductive pathways maintaining ionic conductivity. This composite structure resolves the contradiction between density and conductivity
Solution Approach 2:
The interface film exhibits local quality variations where different regions have different compositions and properties. Sulfate-rich regions provide structural stability while fluorosulfonate-rich regions provide ionic conductivity pathways. This spatial differentiation allows the film to simultaneously achieve density for stability and conductivity for ion transport
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 solution improves the cycle life, storage performance, and cycling performance of lithium secondary batteries by forming a stable interface film that reduces DC internal resistance and inhibits gas production.
Implementation Method 1
the sulfate and the fluosulfonate ions jointly participate in the formation of the positive and negative electrode interface film to form a dense composite film
Implementation Method 2
the formed interface film has strong ionic conductivity
Data Source
AI summary
The present application discloses an electrolyte solution for a lithium secondary battery, a secondary battery, and an electrical device. The electrolyte solution for a lithium secondary battery includes a sulfate and fluorosulfonate ions, and a molar ratio of the sulfate to the fluorosulfonate ions is (8-223):1.