Polymer Solid Electrolyte Composition for Room-Temperature Ion Transport
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Solution Overview
Problem
Polymer solid electrolytes in lithium-ion batteries suffer from low ionic conductivity at room temperature, limiting their application due to poor ion mobility, which is exacerbated by high temperature requirements that increase costs and degrade battery performance.
Innovation Solution
A solid electrolyte composition incorporating a polymer, a lithium salt with a mass content of 30% to 90%, and a small amount of an aprotic organic solvent with a high dielectric constant, which forms lithium ion transmission channels independent of segmental motion, enhancing ionic conductivity without compromising safety or mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature is increased to improve ionic conductivity, then ionic conductivity is improved, but energy density deteriorates and cost increases
Solution Approach 1:
The patent changes the fundamental parameter of ionic conductivity through chemical composition (adding liquid crystalline compounds) rather than relying on temperature parameter adjustment. This allows high ionic conductivity to be achieved at room temperature, eliminating the need for heating systems and preserving energy density.
2Reliability
If lithium salt concentration is increased to improve conductivity, then ionic conductivity is improved, but phase separation occurs and mechanical strength deteriorates
Solution Approach 1:
The liquid crystalline compounds act as intermediaries between the polymer matrix and lithium salts. They facilitate lithium ion transport while maintaining a homogeneous composite structure, preventing phase separation that would occur with high lithium salt concentration in pure polymer electrolytes. The liquid crystalline phase mediates the interaction between polymer and lithium salt, enabling high conductivity without structural degradation.
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 solution significantly improves ionic conductivity at room temperature, reducing the need for elevated temperatures and maintaining mechanical strength, thus enhancing the performance and safety of lithium-ion batteries.
Implementation Method 1
the additive is selected from an aprotic organic solvent with a carbon number lower than 10 and a relative dielectric constant higher than 3.6
Implementation Method 2
a relative dielectric constant higher than 3.6
Implementation Method 3
the lithium ion transport in polymer electrolyte is realized by the swing of the segment, and the ion mobility rate is limited by the swing speed of the polymer segment
Data Source
AI summary
In order to overcome the problem of low ionic conductivity in the existing polymer solid electrolyte, the disclosure provides a solid electrolyte, comprising a polymer, a lithium salt and an additive, the additive is selected from an aprotic organic solvent with a carbon number lower than 10 and a relative dielectric constant higher than 3.6; the mass content of the lithium salt is 30%˜90%, and the mass content of the additive is 0.01%˜2%, based on the total mass of the solid electrolyte being 100%. Further provided is a polymer lithium ion battery comprising the solid electrolyte. According to the solid electrolyte of the disclosure, a trace amount of small molecule aprotic organic solvent with high dielectric constant is introduced as an additive, which can inhibit crystallization of the solid electrolyte, promote transmission of lithium ions in the electrolyte, and improve the ionic conductivity of the solid electrolyte at room temperature.