Composite Separator With Aligned Particle Chains
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Solution Overview
Problem
Conventional porous polymer separators in rechargeable batteries face issues such as flammability and lithium dendrite formation leading to potential fire hazards and internal short circuits, while alternative dense solid electrolyte sheets are inflexible, and composite membranes with randomly dispersed particles are either brittle or poorly conductive.
Innovation Solution
A composite separator with aligned particles, where a high volume fraction of solid electrolyte particles are arranged in chains across the separator thickness, using dielectrophoretic alignment within a polymer matrix, enhancing ionic conductivity while maintaining flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid electrolyte particles are randomly dispersed in the separator, then the separator provides mechanical separation, but the ionic conductivity is poor and the material becomes brittle
Solution Approach 1:
The separator is segmented into distinct regions: a bulk polymer matrix providing mechanical strength and flexibility, and discrete aligned particle chains providing ionic conductivity pathways. This segmentation allows each region to optimize its function without compromising the other.
Solution Approach 2:
Different regions of the separator have different properties: the bulk material provides mechanical properties while the aligned particle regions provide ionic conductivity. This local differentiation resolves the contradiction by assigning different functions to different spatial locations within the same component.
2Reliability
If high volume fraction of particles is used to improve ionic conductivity, then conductivity increases, but the separator becomes brittle and loses flexibility
Solution Approach 1:
The particle volume fraction is localized to specific regions (aligned chains) rather than distributed uniformly throughout the entire separator. This allows high particle concentration (≥85% volume fraction) in conductive pathways while maintaining low overall particle content that preserves bulk material flexibility.
Solution Approach 2:
The separator is a composite structure combining polymer matrix material with solid electrolyte particles in a specific configuration. The composite architecture allows the polymer to provide flexibility while the particle chains provide conductivity, overcoming the limitations of either material alone.
3Reliability
If dense solid electrolyte sheets are used to prevent dendrites, then safety improves, but the separator becomes inflexible
Solution Approach 1:
The separator has localized dense particle regions that provide dendrite resistance and safety, while the bulk polymer matrix maintains flexibility. The aligned particle chains create dense barriers at critical locations without requiring the entire separator to be dense.
Solution Approach 2:
The separator maintains a porous polymer matrix structure that provides mechanical flexibility and ion transport pathways, while aligned particle chains fill specific regions to provide dendrite resistance. This porous architecture prevents the need for completely dense structures.
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 aligned particle structure significantly increases ionic conductivity, reducing the need for high particle loading, thus achieving high performance with moderate loadings, addressing the limitations of conventional and alternative separator technologies.
Implementation Method 1
applying an AC electric field to the particles and the bulk separator material while the bulk separator material is in a liquid state to align the particles into at least one ionically conductive aligned particle region within the bulk separator material
Data Source
AI summary
An ionically conductive composite separator for a rechargeable battery and methods for producing the same are provided. The separator may include a bulk material having an anode side and a cathode side and a thickness extending therebetween and a region of aligned particles extending across the bulk material thickness. The aligned particles may be formed as a particle chain and the particles may be formed of a solid electrolyte material. The ionically conductive separator may be formed by providing a plurality of particles within a bulk material and applying an AC electric field to the particles and the bulk material while the bulk material is in a liquid state to align the particles into at least one ionically conductive aligned particle region within the bulk material.