Roll Press Apparatus for Electrode Sheet Wrinkle Prevention
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Solution Overview
Problem
During the roll pressing of strip-shaped electrode sheets for lithium ion secondary batteries, oblique wrinkles frequently occur at the boundary between active material and absent portions due to uneven tension distribution, causing the active material portion to slacken and concentrate reaction forces on the absent portions.
Innovation Solution
A roll press apparatus with an active-material-absent-portion stretching unit that stretches the active-material absent portions in the longitudinal direction before rolling, ensuring both active material and absent portions are stretched, thereby distributing tension evenly and preventing wrinkles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the strip-shaped electrode sheet is roll-pressed to compress the active material layer, then the active material layer is compacted in the thickness direction, but oblique wrinkles occur in the active-material absent portions near the boundary with the active material portion
Solution Approach 1:
The active-material absent portion stretching unit performs preliminary stretching of the active-material absent portions before the roll pressing process. This preliminary action pre-compensates for the thickness reduction that will occur during compression, ensuring that the active-material absent portions maintain appropriate dimensions and do not develop wrinkles during the subsequent compression process.
Solution Approach 2:
The stretching unit is configured to selectively stretch only the active-material absent portions, while the active material portions are compressed by the roll press. This local differentiation in treatment - stretching in one region and compressing in another - resolves the contradiction by addressing the specific needs of each region to prevent wrinkles while achieving the desired compression.
2Manufacturing precision
If the active material portion is compressed during roll pressing, then the active material layer is densified, but the active-material absent portions are hardly pressed and remain thinner, causing uneven tension distribution
Solution Approach 1:
The active-material absent portion stretching unit performs preliminary stretching before compression, pre-adjusting the thickness of active-material absent portions to compensate for the thickness reduction that will occur during roll pressing. This ensures more uniform thickness distribution in the final compressed product.
Solution Approach 2:
The stretching unit changes the physical parameter (length/thickness) of the active-material absent portions before compression. By adjusting these parameters in advance, the system compensates for the differential compression that occurs during roll pressing, leading to more uniform final dimensions across different portions of the electrode sheet.
3Productivity
If tension is applied to the compressed strip-shaped electrode sheet in the downstream direction, then the electrode sheet is conveyed forward, but the tension concentrates on the active-material absent portions causing reaction forces that generate wrinkles
Solution Approach 1:
The stretching unit performs preliminary deformation of the active-material absent portions before the compression and conveyance processes. This preliminary action modifies the mechanical properties and dimensional stability of these portions, enabling them to better withstand and distribute the tension applied during downstream conveyance without concentrating reaction forces that would cause wrinkles.
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
The solution effectively suppresses the generation of oblique wrinkles in the active-material absent portions by ensuring both the active material and absent portions are stretched, maintaining even tension and preventing reaction force concentration.
Implementation Method 1
an active-material-absent-portion stretching unit arranged upstream of the pair of press rolls and configured to stretch the active-material absent portion of the strip-shaped electrode sheet in the longitudinal direction
Implementation Method 2
a pair of press rolls arranged in parallel with each other with a roll gap, the press rolls being configured to roll-press the strip-shaped electrode sheet being conveyed in the longitudinal direction to compress the active material layer to form the compressed active material layer
Data Source
AI summary
A roll press apparatus for producing a compressed strip-shaped electrode sheet from a strip-shaped electrode sheet including an active material portion and an active-material absent portion is provided with a pair of press rolls arranged in parallel with a roll gap and configured to roll-press the strip-shaped electrode sheet being conveyed in a longitudinal direction for compression to form a compressed active material layer, and an active-material-absent-portion stretching unit arranged upstream of the press rolls and configured to stretch the active-material absent portion of the strip-shaped electrode sheet in the longitudinal direction.