Anisotropic Pore Orientation in Li-Ion Electrodes
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Solution Overview
Problem
Commercially available Li-ion cells have poor materials utilization due to low electrode thickness, leading to limited ion transport and reduced energy delivery, especially in high-rate applications like PHEVs and EVs, where increasing electrode thickness or porosity compromises energy density.
Innovation Solution
The method involves exposing a matrix with fugitive particles or magnetic fluid to a magnetic field to align particles elongately, allowing for the removal of these particles or fluid, creating anisotropic pores that enhance ion transport without reducing energy density, by aligning particles or fluid in the direction of ion diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If electrode thickness is increased to improve energy density, then energy storage capacity is improved, but ion transport capability deteriorates due to increased diffusion pathways
Solution Approach 1:
The electrode structure is segmented into multiple functional zones with different porosity and pore orientation characteristics. The pore structure is divided into through-thickness pores (for ion transport) and lateral pores (for energy storage), allowing independent optimization of transport and storage functions in different spatial regions.
Solution Approach 2:
The invention transitions from conventional isotropic pore structures to anisotropic pore structures with specific orientation. Through-thickness pores are oriented perpendicular to the electrode surface to facilitate ion transport, while lateral pores are oriented parallel to the surface for energy storage, adding directional dimensionality to the pore architecture.
2Reliability
If porosity is increased to improve ion transport, then ion transport capability is improved, but energy density deteriorates due to reduced active material volume
Solution Approach 1:
Different regions of the electrode are assigned different porosity values and pore orientation characteristics. The through-thickness porosity is optimized for ion transport while lateral porosity is optimized for energy storage, allowing local optimization of properties to meet different functional requirements within the same electrode structure.
Solution Approach 2:
The invention utilizes controlled porous structures with specific orientation and distribution characteristics. By creating through-thickness pores and lateral pores with different orientations and porosities, the structure enables simultaneous optimization of ion transport pathways and energy storage capacity.
3Reliability
If tortuosity is decreased to improve ion transport efficiency, then ion transport capability is improved, but manufacturing complexity increases due to difficulty in creating aligned pore structures
Solution Approach 1:
Pore-forming particles are pre-aligned in the desired orientation within the slurry before electrode fabrication. This preliminary alignment of pore formers ensures that the resulting pores will have the correct through-thickness and lateral orientation after processing, simplifying the overall manufacturing process compared to attempting to create aligned pores through complex post-processing steps.
Solution Approach 2:
Pore-forming particles or templates are used as intermediaries to create the desired pore structure. These temporary structures are embedded in the electrode matrix and then removed to leave behind the target pore architecture, making it easier to control pore orientation and tortuosity than direct fabrication methods.
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
This approach increases the tortuosity of electrodes, improving high-rate capability while maintaining energy density, allowing for more efficient ion transport and enhanced battery performance in high-discharge scenarios.
Implementation Method 1
exposing a precursor composition of a porous article to a magnetic field which causes a set of particles in the precursor composition to assume an elongated orientation
Implementation Method 2
exposing a matrix comprising a liquid and fugitive particles to a magnetic field such that the magnetic field causes at least a portion of the fugitive particles to chain
Implementation Method 3
at least partially removing the magnetic fluid from the matrix to form anisotropic pores within the matrix
Data Source
AI summary
The use of magnetic fields in the production of porous articles is generally described. Certain embodiments comprise exposing a matrix to a magnetic field such that particles within the matrix form one or more elongated regions (e.g., one or more regions in which the particles chain). In some embodiments, after the magnetic field has been applied, the particles and/or a liquid within the matrix can be at least partially removed. Removal of the particles and/or the liquid can leave behind anisotropic pores within the remainder of the matrix material.