Cross-Linked Polyelectrolyte Composition for Li-Ion Conductivity
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Solution Overview
Problem
There is a need for a polyelectrolyte composition with improved ionic conductivity, mechanical, and electrochemical properties for next-generation lithium-ion batteries, which existing polyelectrolytes have not adequately addressed.
Innovation Solution
A polyelectrolyte composition comprising a polyionic multiblock polymer with a styrenic block copolymer precursor, a cross-linking agent, a quaternary ammonium salt, and an ionic liquid, specifically designed to enhance ionic conductivity and electrochemical stability, forming a conducting phase with a lithium salt and ionic liquid combination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyelectrolytes are used as electrolytes in Li-ion batteries, then thermal stability and non-flammability are improved, but ionic conductivity is insufficient
Solution Approach 1:
The patent creates a composite polyelectrolyte system combining polyionic multiblock polymer with ionic liquid and lithium salt. The polyionic polymer provides thermal stability and non-flammability, while the ionic liquid component enhances ionic conductivity, achieving both requirements simultaneously through material composition rather than single-material optimization
Solution Approach 2:
The patent optimizes multiple parameters including the molecular weight of polymer blocks (10-100 kg/mol for block D, 5-100 kg/mol for block A), cross-linking agent concentration (0.05-20 mol%), and ionic liquid content to achieve the desired balance between thermal stability and ionic conductivity, with ionic conductivity exceeding 2.0 x 10^-6 S/cm at 30°C
2Strength
If cross-linking agents are added to improve mechanical properties, then structural stability is improved, but device complexity increases
Solution Approach 1:
The patent specifies precise parameter ranges for cross-linking agent concentration (0.05-20 mol% based on total mol of quaternary ammonium salt) to achieve optimal mechanical properties without excessive complexity. This quantitative control transforms a complex compositional variable into a manageable parameter with defined optimization ranges
3Strength
If block copolymer molecular weight is increased to improve mechanical strength, then structural integrity is improved, but processing difficulty increases
Solution Approach 1:
The patent divides the polymer into distinct blocks with specific molecular weight ranges: block D (10-100 kg/mol) containing quaternary ammonium salt, block A (5-100 kg/mol), and optionally block B (1-40 kg/mol) derived from conjugated diene. This segmentation allows each block to contribute specific properties while maintaining overall processability, as smaller individual blocks are easier to handle than a single large molecular weight polymer
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 composition achieves ionic conductivity greater than 2.0 x 10^-6 S/cm at 30°C, improved electrochemical stability, and enhanced discharge capacity, facilitating the development of more efficient lithium-ion batteries with improved performance and cycle retention.
Implementation Method 1
a film obtained from the polyelectrolyte composition has an ionic conductivity at 30°C of greater than 2.0 x 10^-6 S/cm
Data Source
AI summary
A polyelectrolyte composition is disclosed comprising (a) a polyionic multiblock polymer (PILSBC) comprising a styrenic block copolymer (SBC) precursor having at least a quaternary ammonium salt; (b) a cross-linking agent comprising a compound having at least two amino groups; (c) a lithium salt; and (d) an ionic liquid. The SBC precursor comprises at least a block D derived from a substituted vinyl aromatic monomer; a block A derived from a vinyl aromatic monomer; and optionally a block B derived from a conjugated diene monomer. The polyelectrolyte composition has a mol ratio of the ionic liquid to the quaternary ammonium salt of 0.1:1 - 1:1. The polyelectrolyte composition provides improved ionic conductivity and electrochemical properties, and can be used in batteries, e.g., a Li-ion battery.