Flat Wound Electrode Structure to Suppress Battery Springback
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Solution Overview
Problem
The wound electrode body in secondary batteries with a flat shape experiences 'springback' after press-molding, leading to increased thickness, reduced insertability, and localized interelectrode distance variations, which can result in resistance increases and charge carrier precipitation.
Innovation Solution
Incorporating first adhesive layers on the positive electrode and second adhesive layers in the winding start end region of the separators to attach the positive electrode to the separators, thereby reducing the formation of large spaces and local interelectrode distance variations, thus suppressing the occurrence of 'middle cracks'.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the electrode body is press-molded to form a flat shape, then the insertability into the battery case is improved, but the thickness increases due to springback
Solution Approach 1:
The patent applies preliminary action by attaching adhesive layers to the separators before winding. This pre-attachment ensures that when press-molding occurs, the separators remain firmly bonded to the electrodes, preventing springback-induced separation and maintaining consistent thickness without compromising insertability.
Solution Approach 2:
The adhesive layers act as intermediaries between the separators and electrodes. These adhesive layers absorb and distribute the stresses from press-molding and springback, preventing direct separation and maintaining stable interelectrode distances throughout the battery assembly process.
2Shape
If the electrode body is press-molded to form a flat shape, then the overall shape control is improved, but the interelectrode distance varies locally in the flat part
Solution Approach 1:
The patent applies local quality by positioning adhesive layers specifically at the winding start end region of the separators. This localized adhesive application ensures that the critical area where separators contact electrodes maintains consistent bonding, preventing local variations in interelectrode distance while preserving the overall flat shape.
3Reliability
If adhesive layers are added to attach separators to electrodes, then the suppression of middle crack and thickness increase is improved, but the device complexity increases
Solution Approach 1:
The adhesive layers are applied locally only to the winding start end region of the separators, not throughout the entire separator surface. This localized approach provides the necessary bonding to prevent middle cracks and thickness variations while minimizing the addition of structural complexity.
Solution Approach 2:
The adhesive layers replicate the bonding function already present in conventional wound electrode bodies (where adhesion occurs naturally), but apply it in a controlled, localized manner to specifically address the middle crack issue without requiring comprehensive structural modifications.
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 solution effectively suppresses the increase in thickness, resistance, and charge carrier precipitation, while maintaining insertability and battery performance by ensuring consistent interelectrode distances and reducing adhesive layer usage.
Implementation Method 1
the positive electrode includes first adhesive layers on a first surface and a second surface. By the first adhesive layers, the first surface and the first separator are attached to each other and the second surface and the second separator are attached to each other
Implementation Method 2
At least one of the first separator and the second separator includes a second adhesive layer in a winding start end region that exists on a winding start end side relative to a winding start end of the positive electrode, and the first separator and the second separator are attached to each other by the second adhesive layer
Data Source
AI summary
A secondary battery disclosed herein includes a wound electrode body with a flat shape in which a first separator, a negative electrode, a second separator, and a positive electrode are wound. The positive electrode includes first adhesive layers on a first surface and a second surface. By the first adhesive layers, the first surface of the positive electrode and the first separator are attached to each other and the second surface of the positive electrode and the second separator are attached to each other. At least one of the first separator and the second separator includes a second adhesive layer in a winding start end region that exists on a winding start end side relative to a winding start end of the positive electrode. The first separator and the second separator are attached to each other by the second adhesive layer.