SEI Layer Formation via Organo-Polysulfide Additives
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Solution Overview
Problem
Lithium-based batteries face challenges in maintaining the stability of the solid electrolyte interface (SEI) layer, which is crucial for preventing undesirable internal chemical reactions and self-discharge, especially in lithium sulfur and lithium ion batteries.
Innovation Solution
The method involves exposing electrodes to an electrolyte solution containing organo-polysulfide or fluorinated organo-polysulfide additives, applying a voltage or load to form an SEI layer on the electrode surface, where sulfur atoms bond with carbon or other electrode atoms, creating a polymer layer that prevents electrolyte contact and reduces internal reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used in lithium-based batteries, then the batteries can operate and provide energy storage, but the solid electrolyte interface (SEI) layer becomes unstable leading to undesirable internal chemical reactions and self-discharge
Solution Approach 1:
The patent introduces organo-polysulfide or fluorinated organo-polysulfide additives as intermediary substances in the electrolyte solution. These additives mediate the interaction between lithium ions and the electrode surface, facilitating the formation of a stable SEI layer that prevents harmful internal reactions while maintaining battery operation. The additives act as a bridge that enables protective layer formation without compromising the battery's energy storage function.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte solution by incorporating specific organo-polysulfide compounds with defined molecular structures (RSnR′ where n≥2). This parameter change in the electrolyte's chemical makeup triggers a transformation in the SEI layer properties, converting it from unstable to stable and preventing self-discharge while maintaining operational capability.
2Reliability
If the SEI layer is made more protective to prevent internal reactions, then stability improves, but lithium ion transport may be hindered
Solution Approach 1:
The patent creates a SEI layer with spatially differentiated properties through the use of organo-polysulfide additives. The layer exhibits local variations in composition and structure, with regions optimized for protection against internal reactions and other regions that maintain high lithium ion conductivity. This local quality differentiation allows the SEI layer to simultaneously provide robust protection and efficient ion transport pathways.
Solution Approach 2:
The SEI layer formed through the patent's method has a composite structure resulting from the interaction of organo-polysulfide additives with electrode surfaces. This composite material combines protective characteristics that prevent internal reactions with conductive properties that facilitate lithium ion transport, achieving both stability and energy efficiency in a single integrated layer.
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 formed SEI layer enhances the stability and cycling performance of lithium-based batteries by preventing electrolyte consumption and self-discharge, while allowing lithium ion transport, thus improving the battery's capacity and efficiency over cycles.
Implementation Method 1
A voltage or a load is applied to the electrochemical cell... forming an SEI layer on the electrode surface
Implementation Method 2
sulfur atoms bond with carbon or other electrode atoms, creating a polymer layer
Implementation Method 3
allowing lithium ion transport, thus improving the battery's capacity and efficiency over cycles
Data Source
AI summary
In an example of the method for making a solid electrolyte interface (SEI) layer on a surface of an electrode, the electrode is exposed to an electrolyte solution in an electrochemical cell. The electrolyte solution includes either i) an organo-polysulfide additive having a formula RSnR′ (n≥2), wherein R and R′ are independently selected from a methyl group, an unsaturated chain, a 3-(Trimethoxysilyl)-1-propyl group, or a 4-nitrophenyl group, or ii) a fluorinated organo-polysulfide additive having a formula RSnR′ (n≥2), wherein R and R′ can be the same or different, and wherein R and R′ each have a general formula of CxHyF(2x−y+1), where x is at least 1 and y ranges from 0 to 2x. A voltage or a load is applied to the electrochemical cell.