Battery Cell Casing Structure for Weld Crack Resistance
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Solution Overview
Problem
The reliability of battery cells is compromised due to cracking near the welding region between the casing body and the end cap during thermal runaway or excessive gas generation, which affects their performance and safety.
Innovation Solution
The battery cell design includes first walls with a smaller outer surface area than second walls, with a specific dimension ratio and thickened opening portions to enhance strength, reducing the risk of cracking at the welding region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the first wall is made thinner to reduce material usage and weight, then manufacturing cost and weight are reduced, but the strength of the opening portion decreases, increasing the risk of cracking near the welding region
Solution Approach 1:
The opening portion is designed with a greater thickness than the body portion, creating a local quality difference. This thickened opening portion provides enhanced strength and rigidity at the critical welding region while the thinner body portion reduces overall weight and material usage.
Solution Approach 2:
The solution addresses the strength-weight contradiction by transitioning from a uniform 2D wall design to a 3D varying thickness design. The opening portion is extended in the thickness dimension (third direction) to create a stepped structure, adding dimensional complexity to resolve the strength requirement without proportionally increasing weight.
2Reliability
If the first wall dimension ratio W1/W2 is increased to improve structural stability, then the risk of cracking is reduced, but the energy density of the battery cell decreases due to increased material usage
Solution Approach 1:
The design applies local quality enhancement only where needed - the opening portion near the welding region is thickened to improve reliability, while the body portion maintains a thinner profile to preserve energy density. This selective thickening ensures structural integrity without unnecessary material consumption.
Solution Approach 2:
The invention optimizes the dimensional parameters by controlling the ratio W1/W2 within a specific range (0.2-0.6) and setting the thickness ratio between opening and body portions. These parameter changes achieve the balance between reliability improvement and energy density maintenance.
3Reliability
If the opening portion is thickened to reduce cracking risk, then the strength and reliability are improved, but the manufacturing complexity and processing difficulty increase
Solution Approach 1:
The first wall is segmented into two distinct portions: the opening portion with greater thickness and the body portion with smaller thickness. This segmentation allows each portion to be optimized independently - the opening portion for strength and the body portion for weight and manufacturing ease.
Solution Approach 2:
The design employs asymmetry in the wall thickness distribution, creating a stepped structure where the opening portion is thicker than the body portion. This asymmetric design provides enhanced strength at the critical welding region while maintaining overall manufacturability through a relatively simple geometric form.
Data Source
AI summary
Battery cell comprises casing comprising casing body and end cap. Casing body is provided with opening and comprises two first walls arranged opposite to each other in first direction and two second walls arranged opposite to each other in second direction. Area of outer surface of first wall is smaller than area of outer surface of second wall. First wall comprises first opening portion and first body portion distributed in sequence in third direction parallel to thickness direction of end cap. First body portion is far away from opening relative to first opening portion. End cap is connected to first and second walls and seals opening. Dimension W1 of first wall in second direction and dimension W2 of second wall in first direction satisfy 0.2≤W1/W2. Thickness of first opening portion is greater than thickness of first body portion. First, second, and third directions are perpendicular to each other.