PEO Solid Electrolyte High Voltage Stability
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Solution Overview
Problem
Solid-state lithium ion batteries face limitations due to the instability of poly(ethylene oxide) (PEO)-based solid electrolytes at voltages higher than 4.2V, leading to decreased battery performance and limited cycle life, which restricts their widespread adoption.
Innovation Solution
A PEO-based solid electrolyte with a polymer gel formulation that includes a combination of an ethylene oxide polymer and a liquid precursor portion with at least 20 molar percent of a lithium salt, such as lithium bis(trifluoromethanesulfonyl)imide or lithium tetrafluoroborate, which enhances high voltage stability up to 5.5V.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PEO-based solid electrolyte is used, then lithium ion conductivity is improved, but high voltage stability deteriorates above 4.2V
Solution Approach 1:
The patent combines PEO polymer with specific inorganic fillers (such as alumina, silica, or titania nanoparticles) to create a composite solid electrolyte. The inorganic fillers form a stable framework that prevents PEO degradation at high voltages while maintaining lithium ion conductivity pathways through the amorphous regions of the polymer matrix.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating lithium salts (such as LiTFSI or LiBF4) at optimized concentrations alongside PEO. This parameter adjustment creates a formulation that shifts the electrochemical stability window to higher voltages while preserving the necessary ionic conductivity for battery operation.
2Reliability
If solid-state electrolyte is used, then safety is improved, but ionic conductivity is insufficient for practical power performance
Solution Approach 1:
The patent incorporates porous inorganic filler materials with controlled pore structures that facilitate lithium ion transport. These porous fillers create additional conduction pathways and increase the overall ionic conductivity of the solid electrolyte while maintaining the safety advantages of eliminating liquid electrolytes.
Solution Approach 2:
The composite structure combining PEO with conductive inorganic fillers creates synergistic effects where the filler network provides structural stability and additional ion transport channels, achieving both high safety and sufficient ionic conductivity for practical battery applications.
3Productivity
If thin film structures are used, then solid-state battery performance is improved, but energy density decreases
Solution Approach 1:
The patent optimizes the thickness parameter of the solid electrolyte film to a specific range that balances performance and energy density. By controlling the film thickness and composition, the electrolyte achieves sufficient ionic conductivity for high performance while minimizing the volume occupied, thereby preserving overall battery energy density.
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 formulation significantly improves the high voltage stability and cycle life of solid-state batteries, enabling them to perform effectively at higher voltages and extending their operational lifespan.
Implementation Method 1
PEO has the ability to conduct lithium ions as positive lithium ions are solubilized and/or complexed by the ethylene oxide groups on the polymer chain
Implementation Method 2
it is believed that lithium ions move preferentially through the amorphous portion of the PEO material
Data Source
AI summary
An electrochemical cell having an anode, a solid electrolyte, and a cathode. The solid electrolyte includes a polymer gel formed from an ethylene oxide polymer combined with a liquid precursor. The liquid precursor contains at least 15 molar percent of a lithium salt in a solvent.