Interdigitated Li-Ion Electrodes for Stress Relief and Energy Density
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Solution Overview
Problem
Thick electrodes in batteries face mechanical stresses due to stack pressure and internal strain from lithium ion intercalation and de-intercalation, leading to reduced cycling capacity and electrolyte depletion, which decreases volumetric energy density.
Innovation Solution
The use of interdigitated electrodes with different compressibility and microstructures, created through co-extrusion of active materials with varying porosity, forms shorter and less tortuous lithium ion diffusion paths, alleviating mechanical stresses and enhancing energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thick electrodes are used to increase volumetric energy density, then the proportion of active material increases, but mechanical stresses from stack pressure and internal strain cause severe fading of long-term cycling capacity
Solution Approach 1:
The electrode is segmented into multiple thin layers stacked together, with each layer containing active material stripes separated by porous stripes. This segmentation reduces the thickness of individual active material layers, decreasing internal strain and mechanical stress while maintaining high volumetric energy density through the stacked configuration.
Solution Approach 2:
Different regions of the electrode have different properties: active material stripes provide high density and energy storage, while porous stripes provide low density but high porosity for electrolyte penetration and lithium ion diffusion. This local quality differentiation allows the electrode to simultaneously achieve high volumetric energy density and good lithium ion conductivity.
2Quantity of substance
If thick electrodes are used to increase volumetric energy density, then the proportion of active material increases, but electrolyte depletion occurs due to long lithium ion diffusion lengths and poor conductivity
Solution Approach 1:
The electrode is divided into multiple thin layers with porous stripes separating active material stripes. This segmentation creates shorter lithium ion diffusion paths within each layer, reducing electrolyte depletion while maintaining high volumetric energy density through the stacked configuration of multiple layers.
Solution Approach 2:
Porous stripes with high porosity are introduced between active material stripes to provide channels for electrolyte penetration and lithium ion diffusion. These porous regions act as electrolyte reservoirs, ensuring adequate electrolyte supply to thick electrode structures and preventing electrolyte depletion.
3Quantity of substance
If thick electrodes are used to increase volumetric energy density, then inactive material volume decreases, but mechanical stresses from expansion and contraction during charging and discharging increase
Solution Approach 1:
The electrode is segmented into thin layers with porous stripes separating active material stripes. This segmentation reduces the thickness of individual active material layers, decreasing internal strain from expansion and contraction during charging and discharging while maintaining high volumetric energy density through the stacked configuration.
Solution Approach 2:
Porous stripes with low mechanical strength are strategically placed between active material stripes to act as stress-relief zones. These porous regions accommodate expansion and contraction of active material, reducing internal strain and mechanical stress while maintaining the overall thick electrode structure for high volumetric energy density.
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 allows for thicker electrodes with improved lithium ion conductivity and reduced electrolyte depletion, resulting in higher volumetric energy density and extended cycling capacity.
Implementation Method 1
internal strain resulted from the expansion and contraction of the battery electrode as the lithium ions intercalate and de-intercalate into and out of the electrode material during charging and discharging
Implementation Method 2
forms shorter and less tortuous lithium ion diffusion paths
Data Source
AI summary
A battery has an anode, a separator adjacent the anode, and a cathode adjacent the separator opposite the anode, the cathode comprising interdigitated stripes of two different types, one of the types forming pore channels or porous structure and one of the types being more compressible than others type.