Battery Cell End Cover Welding With a Welding Aid Layer
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Solution Overview
Problem
The existing battery cell assembly methods face challenges in controlling the penetration depth during welding of the end cover assembly and current collecting component, leading to risks of false welding, excessive penetration, and potential electrolyte leakage due to cracks, which affect the connection reliability and production quality.
Innovation Solution
The battery cell design includes a first welded portion on the end cover connecting region with a penetration depth equal to or less than the electrode lead-out portion thickness, using materials with different melting points and thermal expansion coefficients, and employing a welding aid layer to improve connection strength and reduce the risk of leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If external penetration welding is used to connect the end cover assembly and current collecting component, then the connection strength is improved, but the penetration depth control becomes difficult leading to false welding or excessive penetration
Solution Approach 1:
A welding aid layer is introduced as an intermediary substance between the end cover assembly and current collecting component during welding. This layer facilitates controlled penetration by regulating molten pool formation and preventing direct metal-to-metal contact that causes uncontrolled penetration, thereby achieving both strong connection and precise penetration depth control
Solution Approach 2:
The welding process parameters are modified by introducing the welding aid layer which changes the thermal and chemical parameters of the welding zone. This layer alters the melting behavior, surface tension, and wetting characteristics of the molten pool, enabling controlled penetration depth while maintaining connection strength
2Reliability
If the penetration depth is increased to ensure adequate melting of the end cover assembly, then the welding reliability is improved, but the risk of excessive penetration and damage to the current collecting component increases
Solution Approach 1:
The welding aid layer serves as a protective intermediary that limits the depth of molten pool penetration. It provides a controlled interface that allows sufficient melting of the end cover assembly for reliable welding while preventing the molten pool from penetrating too deeply and damaging the thinner current collecting component
Solution Approach 2:
The welding aid layer is applied in advance to the welding surface, creating a protective cushion that moderates the welding energy transmission. This pre-applied layer cushions the thermal and mechanical impact, ensuring adequate melting for reliability while preventing excessive penetration damage before the welding process begins
3Strength
If the penetration depth is too large, then the welding connection is strengthened, but the risk of electrolyte solution leakage through cracks increases
Solution Approach 1:
The welding aid layer acts as a mediator that enables strong welding connection through controlled metallurgical bonding while preventing the formation of excessive cracks. By regulating the welding process and molten pool behavior, it ensures adequate connection strength without creating large cracks that could lead to electrolyte leakage
Solution Approach 2:
The introduction of the welding aid layer changes the welding parameters including melting rate, cooling rate, and solidification behavior. These parameter changes result in a weld structure with appropriate strength while minimizing defect formation, particularly cracks that could compromise the sealed structure and cause electrolyte leakage
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 the risk of false welding and electrolyte leakage, enhances connection reliability, and improves the production quality by minimizing defects in the battery cell assembly process.
Implementation Method 1
the welding of the end cover assembly and the current collecting component
Implementation Method 2
a molten pool needs to pass through the relatively thick end cover assembly
Data Source
AI summary
A battery cell includes an electrode assembly, a case, an end cover assembly, and a current collecting component. The electrode assembly includes a first tab. The case is used for accommodating the electrode assembly, and the case has an opening. The end cover assembly covers the opening and is provided with an electrode lead-out portion. The current collecting component includes a tab connecting region and an end cover connecting region. The tab connecting region is used for connecting to the first tab. The end cover connecting region is welded to the inner side of the electrode lead-out portion and forms a first welded portion. The penetration depth of the first welded portion formed on the electrode lead-out portion is smaller than or equal to the thickness of the electrode lead-out portion.