Solid Polymer Electrolyte with Side Chains
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Solution Overview
Problem
Existing solid polymer electrolytes using high molecular weight polyethylene oxide suffer from low ion conductivity at room temperature due to high crystallinity, which restricts lithium ion migration, and high molecular weight polymers result in decreased mechanical strength and conductivity at elevated temperatures.
Innovation Solution
A solid polymer electrolyte comprising a lithium salt and a polymer with specific repeating units, including a phenyl group and low molecular weight polyethylene oxide groups introduced to side chains, which enhances ion conductivity and mechanical strength by reducing crystallinity and improving film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight polyethylene oxide is used to prepare solid polymer electrolyte, then mechanical strength is improved, but ion conductivity decreases to 10^-5 S/cm
Solution Approach 1:
The patent changes the molecular weight parameter of polyethylene oxide from high to low (10^4-10^6 g/mol range), which fundamentally alters the crystallinity and ion conductivity characteristics of the solid polymer electrolyte, achieving both high mechanical strength and high ion conductivity simultaneously
Solution Approach 2:
The patent creates a composite solid polymer electrolyte system by combining low molecular weight polyethylene oxide with specific lithium salts (LiClO4, LiBF4, LiPF6) in optimized ratios, where the composite structure achieves synergistic effects that improve both mechanical properties and ion conductivity beyond what single components can provide
2Reliability
If low molecular weight polyethylene oxide is used to prepare solid polymer electrolyte, then ion conductivity is improved at room temperature, but liquidization occurs due to polymer being present with salt
Solution Approach 1:
The patent optimizes the molecular weight parameter of polyethylene oxide to a specific low range (10^4-10^6 g/mol) and controls the lithium salt content within 10-50 wt%, which prevents liquidization while maintaining high ion conductivity at room temperature
Solution Approach 2:
The patent introduces side chains with specific local structures (fluorinated groups, cyclic structures) into the polyethylene oxide backbone, creating local regions with enhanced interaction with lithium ions that prevent liquidization while maintaining overall high ion conductivity
3Strength
If high molecular weight polyethylene oxide is used, then mechanical strength is maintained, but ion conductivity decreases due to high crystallinity restricting lithium ion migration
Solution Approach 1:
The patent changes the molecular weight parameter to low range and controls crystallinity content to 20-80%, which reduces the restriction on lithium ion migration while maintaining adequate mechanical strength through optimized composite structure
Solution Approach 2:
The patent introduces lithium salts as intermediary substances that facilitate ion transport through the polyethylene oxide matrix, creating conductive pathways that bypass crystalline regions and enable high ion conductivity even with maintained mechanical strength
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 achieves high ion conductivity (5x10^-5 to 5x10^-4 S/cm at room temperature) and mechanical strength, enabling enhanced electrochemical safety and stability in lithium secondary batteries across a wide temperature range.
Implementation Method 1
by including a polymer having a polyethylene oxide group introduced to a side chain, the solid polymer electrolyte according to one embodiment of the present invention is capable of enhancing ion conductivity at room temperature by lowering crystallinity of the solid polymer electrolyte
Implementation Method 2
a lithium secondary battery using a gel polymer electrolyte preventing leakage of an electrolyte liquid by containing an electrolyte liquid and a salt in a polymer
Data Source
Figure 1~2
AI summary
The present invention relates to a solid polymer electrolyte having high mechanical strength and ion conductivity, and a lithium secondary battery including the same.