Composite Polymer Electrolytes for Stable SEI in Li-Ion Cells
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Solution Overview
Problem
Conventional organic solvent-based electrolytes in Li-ion batteries with silicon anodes and high-voltage nickel-rich cathodes face issues such as unstable solid electrolyte interphase (SEI) layers, volume expansion, oxidative instability, transition metal ion dissolution, and poor cycling stability, leading to safety concerns and performance degradation.
Innovation Solution
Employing a blend-based membrane comprising two or more polymer electrolytes, such as PEO/PMVMA/PVA, and fillers like SiO2, to stabilize the interphase between the electrodes, forming a stable SEI layer and enhancing mechanical and thermal properties, thereby improving safety and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional organic solvent-based electrolytes are used in Li-ion batteries with silicon anodes, then the batteries can achieve high energy density, but the solid electrolyte interphase (SEI) layer becomes unstable and the batteries exhibit poor cycling stability
Solution Approach 1:
The patent uses a composite polymer electrolyte system combining multiple polymers (PEO, PMVMA, PVA) with inorganic fillers (SiO2, Al2O3, TiO2) to create a stable SEI layer that maintains cycling stability while enabling high energy density through silicon anodes. The composite structure provides both mechanical stability and ionic conductivity.
Solution Approach 2:
The patent modifies the electrolyte composition by incorporating specific ratios of polymer electrolytes and inorganic fillers, changing the physical and chemical parameters of the electrolyte system to achieve optimal SEI stability and ion conductivity for long-term cycling performance.
2Quantity of substance
If silicon-based anodes are used to increase energy density, then the volumetric capacity improves, but the large volumetric expansion during lithiation causes disintegration of active material
Solution Approach 1:
The patent employs a flexible polymer electrolyte membrane that can accommodate the volumetric expansion of silicon anodes during lithiation. The polymer matrix provides a compliant structure that prevents mechanical disintegration of the active material while maintaining electrical contact and ionic conductivity.
Solution Approach 2:
The composite polymer electrolyte with inorganic fillers creates a mechanically robust yet flexible structure that supports silicon anodes during volume changes, preventing disintegration while maintaining structural integrity throughout cycling.
3Quantity of substance
If high-voltage nickel-rich cathodes are paired with silicon anodes to improve energy density, then the battery capacity increases, but transition metal ion dissolution and oxidative instability occur
Solution Approach 1:
The polymer electrolyte acts as an intermediary between the high-voltage nickel-rich cathode and silicon anode, providing a stable interface that prevents direct harmful interactions. The electrolyte composition suppresses transition metal ion dissolution and reduces oxidative instability while maintaining high capacity operation.
4Speed
If organic liquid electrolytes are used in Li-ion batteries, then the ionic conductivity is high, but safety issues arise due to volatilization, flammability and explosion
Solution Approach 1:
The patent changes the physical state of the electrolyte from liquid to solid polymer gel, fundamentally altering safety properties while maintaining ionic conductivity through the polymer matrix structure and incorporated liquid electrolyte phases within the gel network.
Solution Approach 2:
The composite polymer gel electrolyte combines solid polymer matrix with liquid electrolyte components, achieving both high ionic conductivity from the liquid phase and safety from the solid polymer structure that prevents volatilization and flammability.
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 proposed electrolyte system stabilizes the SEI layer, reduces impedance, and enhances Li+-ion conductivity, resulting in improved cycling stability and safety of Li-ion batteries with silicon anodes and high-voltage cathodes.
Implementation Method 1
Achieving stable cycling is hampered due to the large volume changes and unstable solid electrolyte interphase (SEI) layer of the Si-anode in liquid organic electrolytes
Implementation Method 2
a blend-based membrane comprising two or more polymer electrolytes, such as PEO/PMVMA/PVA, and fillers like SiO2, to stabilize the interphase between the electrodes, forming a stable SEI layer and enhancing mechanical and thermal properties
Implementation Method 3
at least one filler... enhances Li+-ion conductivity
Data Source
AI summary
Energy storage devices comprising blend-based polymer electrolytes, a salt, and at least a filler are disclosed. The energy storage device comprises a first electrode and a second electrode, a blend-based membrane between the first electrode and the second electrode comprising two or more polymer electrolytes, and at least one filler.