Crown Ether Electrolyte for Stable SEI in Silicon Li-Ion Batteries
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Solution Overview
Problem
Silicon-based anodes in lithium-ion batteries face challenges such as large volumetric expansion leading to disintegration of active material, loss of electrical conduction paths, unstable solid electrolyte interphase (SEI) layer formation, oxidative instability of conventional non-aqueous electrolytes, and inferior cycle life, while high-voltage cathodes like NCM or LCO suffer from unstable surface layers, electrolyte decomposition, and thermal instability.
Innovation Solution
The use of a crown ether based compound in combination with linear and cyclic carbonates and a Li-containing salt forms a stable SEI layer on Si anodes, modifies cathode surfaces, and enhances thermal stability, thereby improving the electrochemical performance and safety of Si-based anode//NCM or LCO cathode Li-ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anodes are used to increase energy density, then capacity is improved, but volumetric expansion leads to disintegration of active material and loss of electrical conduction paths
Solution Approach 1:
The patent applies preliminary action by forming a stable solid electrolyte interphase (SEI) layer on the silicon anode surface before significant expansion occurs. The electrolyte composition with crown ether-based compounds and specific carbonate ratios pre-treats the silicon surface, creating a protective layer that prevents subsequent disintegration during cycling, thus maintaining both high capacity and long cycle life
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by incorporating crown ether-based compounds (0.1-10 wt%) and optimizing the ratio of linear to cyclic carbonates. This parameter modification alters the properties of the SEI layer formed on silicon, making it more stable and less prone to disintegration during volumetric expansion, thereby resolving the contradiction between high capacity and cycling stability
2Quantity of substance
If silicon-based anodes are used to increase energy density, then capacity is improved, but unstable SEI layer formation occurs leading to irreversible capacity loss
Solution Approach 1:
The electrolyte composition with crown ether-based compounds performs preliminary stabilization of the SEI layer formation process. By pre-conditioning the electrolyte environment with these compounds, the patent ensures that the SEI layer forms with stable composition and structure from the beginning, preventing subsequent instability and the associated irreversible capacity losses during cycling
Solution Approach 2:
The crown ether-based compounds act as intermediaries that mediate between the silicon anode and the bulk electrolyte. These compounds facilitate the formation of a stable SEI layer by interacting with silicon surfaces and regulating the decomposition of carbonate solvents, thereby reducing irreversible capacity loss while maintaining high capacity
3Use of energy by moving object
If conventional non-aqueous electrolytes are used, then electrochemical performance is achieved, but oxidative instability occurs at voltages beyond 4.5 V
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by incorporating crown ether-based compounds and optimizing carbonate ratios. These parameter modifications increase the oxidative stability of the electrolyte, allowing it to maintain reliability at high voltages beyond 4.5 V while preserving good electrochemical performance
4Quantity of substance
If high-voltage cathodes like NCM or LCO are used to increase energy density, then capacity is improved, but unstable surface layers and electrolyte decomposition occur
Solution Approach 1:
The crown ether-based compounds in the electrolyte act as intermediaries that interact with the cathode surface. They modify the surface layer composition and structure of high-voltage cathodes like NCM and LCO, creating a more stable interface that prevents electrolyte decomposition and maintains reliability while preserving high 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 electrolyte system stabilizes the Si anode, reduces volume expansion, prevents electrolyte decomposition, and increases thermal stability, resulting in improved cycle life and safety of Si-based anode//NCM or LCO cathode Li-ion batteries.
Implementation Method 1
an unstable solid electrolyte interphase (SEI) layer can develop on the surface of the cycled anodes
Implementation Method 2
oxidative instability of the conventional non-aqueous electrolyte takes place at voltages beyond 4.5 V
Data Source
AI summary
Electrolytes and electrolyte additives for energy storage devices comprising crown ether based compounds are disclosed. The energy storage device comprises a first electrode and a second electrode, wherein at least one of the first electrode and the second electrode is a Si-based electrode, a separator between the first electrode and the second electrode, an electrolyte comprising at least two electrolyte co-solvents, wherein at least one electrolyte co-solvent comprises a crown ether based compound.