Electrode Base Sheet Roughness for Precise Active Material Boundaries
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Solution Overview
Problem
The irregular shape and irregularities at the boundary between coated and non-coated areas of an electrode's active material film, caused by mask peeling and coating material entry into gaps, result in reduced shape precision and potential chipping, which are not effectively addressed by existing methods.
Innovation Solution
A method involving a base sheet with alternating smooth and rough regions, where the active material film selectively adheres to the smooth regions, eliminating the need for masks and enhancing shape precision through controlled surface roughness and adhesion, using wet powder to form the film and ultrasonic joining for the current-collecting member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a mask is used to form coated and non-coated areas by continuous application, then the application process can be continuous, but the mask may excessively adhere to the base sheet causing gaps and irregularities at the boundary
Solution Approach 1:
The base sheet is designed with different surface roughness in different regions: a first region with lower arithmetic mean roughness where the active material film should adhere, and a second region with higher arithmetic mean roughness where the film should not adhere. This local differentiation of surface properties enables selective adhesion, allowing continuous application without masks while preventing excessive adhesion and boundary irregularities.
2Strength
If the mask adheres strongly to the base sheet to prevent gaps, then adhesion is improved, but the active material film may enter gaps and cause irregularities at the end portion
Solution Approach 1:
By creating regions with different surface roughness on the base sheet, the invention achieves uniform adhesion strength across the coated area without needing strong overall mask adhesion. The controlled roughness difference ensures the active material film adheres uniformly to the first region while being repelled from the second region, eliminating gap formation and boundary irregularities.
3Manufacturing precision
If discontinuous application is used to form coated and non-coated areas, then the boundary shape can be controlled, but the operation becomes intermittent and less efficient
Solution Approach 1:
The invention enables continuous application by using a base sheet with spatially differentiated surface roughness. The application process can proceed continuously across the entire base sheet because the selective adhesion is determined by the pre-formed roughness pattern rather than by intermittent masking or stopping. This maintains high productivity while achieving precise boundary control.
4Manufacturing precision
If a mask is used to define coated areas, then shape precision can be achieved, but the process complexity and cost increase
Solution Approach 1:
Instead of using masks to define coated areas, the invention incorporates the patterning function directly into the base sheet through localized surface roughness modification. This eliminates the masking step entirely, reducing process complexity and cost while maintaining the ability to precisely define coated and non-coated areas through the roughness pattern.
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 improves shape precision at the film's end portion, simplifies the process, reduces costs, and enhances joining strength, while allowing for continuous application without irregularities.
Implementation Method 1
an active material film may selectively adhere to a smooth surface
Implementation Method 2
The arithmetic mean roughness of the second region is greater than an arithmetic mean roughness of the first region
Implementation Method 3
ultrasonic joining for the current-collecting member
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method of producing an electrode comprises (a) to (c) below: (a) preparing a base sheet; (b) preparing an active material film; and (c) affixing the active material film to the base sheet by passing the base sheet and the active material film through a roll gap. The base sheet includes a first region and a second region. An arithmetic mean roughness of the second region is greater than an arithmetic mean roughness of the first region. The second region is adjacent to the first region. In the (c), the active material film adheres selectively to the first region among the first region and the second region.