Secondary Battery Electrode Surface Structure for Ion Diffusivity
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Solution Overview
Problem
Conventional methods for producing secondary battery electrodes result in improved ion diffusivity due to many interparticle voids, but they fail to achieve sufficient energy density, and the formation of optimal concavities/convexities for ion diffusivity is hindered by insufficient film formation.
Innovation Solution
A secondary battery electrode with a concave/convex shape on its surface, featuring linear cracks unevenly distributed in the concave portions, is developed. This configuration allows for suitable introduction of Li ions around the cracks and maintains high energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional film formation methods are used to produce electrode active material layer, then production process is simple, but ion diffusivity is insufficient due to lack of optimal concavities/convexities
Solution Approach 1:
The patent applies preliminary action by forming concavities and convexities on the coating film surface before drying. This pre-structuring creates optimal pathways for ion diffusion that are preserved through the drying and pressing processes, thereby improving ion diffusivity without requiring complex post-processing steps.
Solution Approach 2:
The patent implements local quality by creating non-uniform surface structures with specific concavities and convexities in different regions of the electrode. This localized structural variation optimizes ion diffusion pathways in specific areas while maintaining high energy density in others, resolving the contradiction between simple process and improved ion diffusivity.
2Reliability
If many interparticle voids are created to improve ion diffusivity, then ion diffusivity is improved, but energy density becomes insufficient
Solution Approach 1:
The patent applies local quality by creating specific concave and convex regions with controlled void distributions. Concave portions contain interparticle voids that facilitate ion diffusion, while convex portions maintain higher density for energy storage. This spatially differentiated structure resolves the contradiction between ion diffusivity and energy density.
Solution Approach 2:
The patent segments the electrode surface into distinct concave and convex regions with different functional characteristics. This segmentation allows independent optimization of ion diffusion pathways in concave areas and energy density in convex areas, thereby resolving the trade-off between these two parameters.
3Reliability
If concavities/convexities are formed during film formation, then optimal structure for ion diffusivity is achieved, but film formation becomes insufficient
Solution Approach 1:
The patent forms concavities and convexities as a preliminary step before drying and pressing. This timing allows the structural features to be established when the coating material is still pliable, ensuring proper formation without compromising film quality. The subsequent drying and pressing steps then preserve these features while achieving proper film density.
Data Source
AI summary
An electrode having both high energy density and ion diffusivity includes an electrode active material layer on either a positive-or negative-electrode current collector, in which the electrode active material layer has a concave/convex shape on its surface in a predetermined pattern at a constant pitch. In a cross-sectional SEM image of the electrode active material layer, linear cracks are unevenly distributed in a concave portion compared to in a convex portion.