Polymer electrolyte and preparation method therefor
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Solution Overview
Problem
Poly(ethylene oxide) (PEO)-based electrolytes exhibit extremely low ion conductivity at temperatures below their melting point due to high crystallinity, limiting their application in lithium batteries.
Innovation Solution
A polymer electrolyte with reduced crystallinity is developed by introducing nitrogen or phosphorus compound functional groups at the terminals of PEO, enhancing ion conductivity and lithium cation transference without altering the molecular weight of PEO, and doping with lithium salts to achieve improved conductivity and transference characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PEO-based electrolyte is used to achieve high stability, then stability is improved, but ion conductivity becomes extremely low at room temperature due to high crystallinity
Solution Approach 1:
The patent applies local quality by introducing functional groups (nitrogen or phosphorus compounds) specifically at the terminal positions of PEO chains rather than throughout the entire polymer structure. This localized modification reduces crystallinity at the chain ends while preserving the stable PEO backbone structure, thereby achieving both high stability and improved ion conductivity at room temperature
Solution Approach 2:
The patent changes the chemical parameters of the PEO electrolyte by incorporating lithium salts (such as LiTFSI, LiBF4, LiPF6) and terminal functional groups. This parameter change transforms the electrolyte from a highly crystalline state with low ion conductivity to a modified state with reduced crystallinity and enhanced ion conductivity at room temperature while maintaining the inherent stability of PEO
2Manufacturing precision
If terminal functional groups are introduced to reduce crystallinity, then ion conductivity is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the PEO polymer structure into distinct functional regions: the main chain retains the original PEO structure for stability, while the terminal positions are segmented as separate functional units with nitrogen or phosphorus compounds. This segmentation allows independent optimization of each region's properties without complicating the overall device architecture
Solution Approach 2:
The patent creates a composite material system by combining PEO base polymer with lithium salts and terminal functional groups containing nitrogen or phosphorus compounds. This composite approach achieves improved ion conductivity through the synergistic interaction of components while maintaining a relatively simple overall structure that does not significantly increase device complexity
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 modified polymer electrolyte demonstrates excellent room temperature ion conductivity and enhanced lithium cation transference, leading to improved discharge capacity and charging/discharging speed in lithium batteries.
Implementation Method 1
a poly(ethylene oxide) (PEO) containing polymer which is a novel polymer capable of reducing the crystallinity of the polymer
Implementation Method 2
exhibits excellent room temperature ion conductivity and has been improved in transference number of lithium cations
Data Source
Figure 1
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AI summary
The present invention relates to a polymer electrolyte comprising a poly(ethylene oxide)(PEO)-based polymer; and a lithium salt, wherein the terminal of the poly (ethylene oxide) polymer is substituted with a sulfur compound functional group, a nitrogen compound functional group or a phosphorus compound functional group, and a method for preparing the same.