Battery Electrode Warpage Correction via Roller Tensile Force
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Solution Overview
Problem
The production of electrodes for batteries faces challenges due to residual stress and warpage caused by differences in elongation between coated and uncoated portions of the current collector, leading to distortion, wrinkles, cracks, and reduced yield, especially during the lamination and winding processes.
Innovation Solution
A method involving compression-molding and applying tensile force to a strip electrode plate with a current collector exposed portion positioned on a step portion of a roller and the active material-containing layer on a recessed portion, allowing concentrated tensile force on the exposed portion to correct distortion and warpage, thereby preventing electrode breakage and improving quality and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the current collector is compressed by a roll press machine to increase active material density, then the battery capacity is improved, but residual stress and warpage occur due to differential elongation between coated and uncoated portions
Solution Approach 1:
The current collector is divided into coated and uncoated portions with distinct functional requirements. The uncoated portion serves as a stress compensation zone that is intentionally left without active material so it can elongate more during compression, counterbalancing the shrinkage of the coated portion and maintaining overall electrode flatness.
Solution Approach 2:
Different regions of the current collector are given different properties: the coated portion contains active material for electrochemical function while the uncoated portion is stripped of active material to serve purely as a mechanical stress buffer. This local differentiation allows each region to perform its specific function optimally.
2Manufacturing precision
If the uncoated current collector is stretched by plastic deformation to compensate for warpage, then electrode flatness is improved, but the risk of electrode breakage increases due to high tensile stress
Solution Approach 1:
The uncoated current collector is pre-stretched during the compression molding process itself, before the electrode is wound or subjected to additional mechanical stress. This preliminary plastic deformation pre-compensates for the shrinkage that will occur during winding, reducing the risk of breakage in subsequent handling.
Solution Approach 2:
The uncoated portion acts as a built-in stress buffer that absorbs and compensates for dimensional changes during compression and winding. This cushioning effect prevents excessive stress from concentrating on the coated portion, thereby protecting against electrode breakage.
3Manufacturing precision
If a groove is formed on the press roll to compress both coated and uncoated portions simultaneously, then electrode flatness is improved, but the press roll requires frequent repolishing due to abrasion
Solution Approach 1:
The uncoated active material is extracted from the current collector surface in specific regions, creating uncoated portions that can be compressed without the complications of having active material present. This eliminates the need for grooved press rolls while still achieving differential compression to maintain flatness.
4Manufacturing precision
If tensile stress is applied to plastically deform the current collector for stretching, then electrode flatness is improved, but the required stress is several times the original winding stress, risking electrode breakage
Solution Approach 1:
The compression pressure and temperature parameters are optimized to enable effective compression of the active material-containing layer while minimizing differential elongation. By controlling these parameters, the need for high-magnitude subsequent tensile stress is reduced, lowering the risk of electrode breakage.
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 effectively reduces distortion and warpage, preventing electrode breakage and enhancing the quality and productivity of battery electrodes by concentrating tensile force on the current collector exposed portion, ensuring high accuracy and reduced stress on the active material-containing layer.
Implementation Method 1
the current collector is further plastically deformed by tensile stress to stretch the current collector
Implementation Method 2
applying tensile force to the strip electrode plate in a longitudinal direction of the strip electrode plate
Data Source
AI summary
According to one embodiment, a method for producing an electrode, includes applying tensile force. The electrode includes a strip current collector, a current collector exposed portion, and an active material-containing layer. In the applying tensile force, arranging a strip electrode plate on a roller including a step portion and a recessed portion such that the current collector exposed portion is positioned on the step portion and the active material-containing layer is positioned on the recessed portion, and then applying tensile force to the strip electrode plate in a longitudinal direction of the strip electrode plate.