Battery Cap Assembly Terminal Segmentation and Sealing
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Solution Overview
Problem
In secondary batteries, the connection between copper and aluminum terminal posts is prone to failure due to welding difficulties, leading to leakage and low energy density, with the existing friction welding method being complex and costly.
Innovation Solution
A cap assembly with a composite first electrode terminal comprising different base metals, where the second terminal board covers the electrode lead-out hole and is connected to the cap plate, reducing tensile stress and using a sealing member to enhance sealing and reduce internal space occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If friction welding is used to connect copper and aluminum terminal posts, then the connection between different materials is achieved, but the manufacturing process becomes complex and costly
Solution Approach 1:
The terminal post is divided into two separate parts: a copper terminal post for the negative electrode and an aluminum terminal post for the positive electrode. This segmentation eliminates the need for friction welding between dissimilar materials, simplifying the manufacturing process while maintaining connection reliability through separate, material-appropriate welding procedures.
Solution Approach 2:
The cap plate serves as an intermediary component that connects the copper negative electrode terminal post and the aluminum positive electrode terminal post. This mediator allows each terminal post to be made from its optimal material without requiring direct welding between copper and aluminum, thus avoiding the complexity of friction welding while ensuring reliable connections.
2Reliability
If the negative electrode terminal post extends inside the shell for sealing ring installation, then sealing is improved, but space utilization decreases and energy density is reduced
Solution Approach 1:
The sealing ring is extracted from its traditional position inside the shell and relocated to the cap plate. The sealing ring is installed between the cap plate and the negative electrode terminal post, outside the shell. This extraction eliminates the need for the terminal post to extend inside the shell, maximizing space utilization and energy density while maintaining effective sealing.
Solution Approach 2:
The sealing function is moved from the radial dimension (inside the shell) to the axial dimension (at the cap plate interface). By placing the sealing ring at the cap plate where it can be compressed between the cap plate and terminal post, sealing effectiveness is maintained without consuming valuable internal shell space, thus improving energy density.
3Reliability
If the sealing ring is compressed to improve sealing, then sealing performance is enhanced, but tensile stress accumulates at the connection interface causing potential fracture
Solution Approach 1:
The cap plate acts as an intermediary that absorbs and distributes the compressive force from the sealing ring. By positioning the sealing ring between the cap plate and the terminal post flange, the cap plate mediates the stress, preventing direct transmission of tensile stress to the vulnerable connection interface between the terminal post and electrode, thus maintaining both sealing performance and connection strength.
Solution Approach 2:
The cap plate provides a cushioning effect by absorbing the compressive stress from the sealing ring before it can be transmitted to the terminal post connection interface. This beforehand cushioning prevents the accumulation of tensile stress at the connection interface, reducing the risk of fracture while maintaining effective sealing.
4Adaptability or versatility
If copper and aluminum materials are used for different electrode terminals, then material properties are optimized, but welding difficulty increases due to different melting points and specific heat capacities
Solution Approach 1:
The terminal posts are segmented by material type, with the negative electrode terminal post made of copper and the positive electrode terminal post made of aluminum. This segmentation allows each terminal post to be optimized for its specific material properties without requiring difficult copper-aluminum welding, as each can be welded to its corresponding busbar using material-appropriate welding processes.
Solution Approach 2:
The cap plate serves as an intermediary that connects the copper and aluminum terminal posts without requiring direct welding between these dissimilar materials. This mediator enables the system to benefit from material-optimized terminal posts while avoiding the welding difficulties associated with joining copper and aluminum directly.
Data Source
AI summary
The present disclosure provides a cap assembly for a secondary battery, a secondary battery and a battery module. The cap assembly for the secondary battery includes a cap plate, a first electrode terminal, and a sealing member, wherein: the cap plate has an electrode lead-out hole; the first electrode terminal includes a first terminal board and a second terminal board connected with the first terminal board, wherein the first terminal board is located at a side of the second terminal board away from the cap plate, the second terminal board covers the electrode lead-out hole, and the material of the first terminal board and the material of the second terminal board have different base metals; the sealing member surrounds the electrode lead-out hole and is disposed between the cap plate and the first electrode terminal to seal the electrode lead-out hole.