Secondary Battery Cap Assembly Recess for Flush Side Welding
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Solution Overview
Problem
Surface unevenness caused by welding beads on the cap assembly of secondary batteries can lead to connection failures at the positive and negative electrodes, affecting the reliability and performance of the battery module.
Innovation Solution
Incorporating a welding recess at the side portion of the cap assembly and the battery can, allowing for top surface welding and maintaining a uniform size after welding, thereby preventing weld beads from protruding and ensuring even contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If top surface welding is used to join the cap assembly to the battery can, then the bonding strength is improved, but surface unevenness occurs due to weld bead protrusion
Solution Approach 1:
The cap assembly incorporates a welding recess at the specific location where welding occurs, creating a localized depression that accommodates the weld bead. This local structural modification allows the welding area to have different geometry from the rest of the cap assembly, enabling weld bead containment while maintaining the overall integrity and flatness of the cap assembly surface.
Solution Approach 2:
The welding recess is pre-formed on the cap assembly before the welding process. This preliminary structural preparation ensures that when welding occurs, the weld bead will be contained within the recessed area, preventing surface protrusion and maintaining surface uniformity from the outset rather than requiring post-welding correction.
2Reliability
If welding is performed on the cap assembly, then the cap assembly is securely bonded to the battery can, but connection failures occur due to surface unevenness
Solution Approach 1:
The welding recess creates a localized depression at the welding interface, allowing the weld bead to be contained within this specific area. This ensures that the bonding process achieves strong adhesion while the surrounding contact surfaces remain flat and uniform, preventing connection failures caused by surface irregularities.
Solution Approach 2:
The welding process inherently produces weld beads that cause surface protrusion, but by designing a welding recess, the harmful protrusion is converted into a beneficial feature where the weld bead fills the recessed area. This transforms the potential defect into a positive bonding structure that enhances connection reliability while maintaining surface uniformity.
3Manufacturing precision
If the cap assembly width is reduced to fit within the battery can, then the uniform size after welding is improved, but the cap assembly structure becomes more constrained
Solution Approach 1:
Instead of reducing the cap assembly width in the horizontal dimension, the solution introduces a vertical dimension by creating a welding recess (a depression in the depth direction). This allows the cap assembly to maintain its original width while still achieving uniform size after welding, as the recess accommodates the weld bead vertically rather than requiring horizontal compression.
Solution Approach 2:
The cap assembly is segmented into different functional zones: the main body portion that maintains electrical connection functions, and the welding recess portion that handles the bonding function. This segmentation allows each zone to be optimized independently, with the recess providing the necessary structural accommodation for welding without compromising the overall cap assembly design.
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 enhances the stability and yield of secondary batteries by preventing connection failures and maintaining a uniform width, which simplifies the alignment of adjacent battery cells in a module, increasing density and reliability.
Implementation Method 1
a cap assembly electrically connected to the positive electrode plate and the negative electrode plate, and having a welding recess at a peripheral portion of the cap assembly, the cap assembly being joined to a welding end of the battery can via the welding recess
Data Source
AI summary
A secondary battery includes: a battery can having an opening to expose an accommodating space, a can width in a first direction, and a can length in a second direction crossing the first direction; an electrode assembly in the accommodating space, and including a positive electrode plate, a negative electrode plate, and a separator therebetween; a cap assembly electrically connected to the positive electrode plate and the negative electrode plate, and having a welding recess at a peripheral portion, the cap assembly being joined to a welding end of the battery can via the welding recess to seal the accommodating space; and a side weld joining a side portion of the welding end to a side portion of the cap assembly, a surface of the side weld being located at a same level as or a level lower than that of an outer peripheral surface of the battery can.