Button Cell Cap Plate Bonding Without Separator Heat Damage
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Solution Overview
Problem
Conventional button cells face issues with separator damage due to welding heat and potential short circuits between electrodes, especially in ultra-small rechargeable batteries used in wearable devices and wireless communication applications.
Innovation Solution
A button cell design featuring a cap plate that is insulated and bonded to the case using a non-welding method, with a bonding layer that covers the opening and prevents protrusion, thereby avoiding direct contact and heat damage, and includes a step part and edge configuration to ensure secure sealing without welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cap plate is welded to the case while the electrode assembly is accommodated inside the case, then the bonding strength between cap plate and case is improved, but the separator included in the electrode assembly may be damaged due to welding heat, resulting in a short circuit between the first electrode and the second electrode
Solution Approach 1:
The bonding layer is divided into multiple segments: a first bonding layer between the cap plate and side wall, and a second bonding layer between the cap plate and bottom surface. This segmentation allows the bonding function to be distributed across multiple locations, reducing the heat concentration at any single welding point and preventing separator damage while maintaining overall bonding strength.
Solution Approach 2:
The bonding layer acts as an intermediary substance between the cap plate and the case (side wall and bottom surface). Instead of directly welding the cap plate to the case, the bonding layer mediates the connection, providing mechanical bonding without generating harmful welding heat that could damage the separator.
2Reliability
If the cap plate protrudes to the outside of the side wall of the case, then the sealing performance is improved, but the button cell becomes vulnerable to external interference and damage
Solution Approach 1:
The cap plate is nested within the case structure, with the first bonding layer positioning the cap plate against the side wall and the second bonding layer securing it to the bottom surface. This nested configuration allows the cap plate to be firmly integrated into the case without protruding outward, maintaining sealing performance while protecting against external interference.
Solution Approach 2:
The protrusion function is extracted from the cap plate design. Instead of relying on cap plate protrusion for sealing, the sealing function is achieved through the bonding layer configuration and the cap plate's integration within the case boundaries, eliminating the vulnerability to external interference.
3Object-affected harmful factors
If a bonding layer is introduced between the cap plate and the case to prevent welding heat damage, then the separator protection is improved, but the device complexity increases
Solution Approach 1:
The bonding layer serves multiple functions simultaneously: it provides mechanical bonding between the cap plate and case, acts as thermal insulation to protect the separator from heat, and contributes to the overall structural integrity. This multi-functionality reduces the need for additional protective components, thereby limiting the increase in device complexity.
Solution Approach 2:
The bonding function and protective function are merged into a single bonding layer component. Instead of having separate bonding elements and protective elements, the bonding layer combines both roles, simplifying the overall structure while achieving separator protection without excessive complexity increase.
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
Prevents damage from welding heat and external interference, ensuring the integrity of the separator and preventing short circuits between electrodes, thus enhancing the reliability and durability of the button cell.
Implementation Method 1
a bonding layer located between the cap plate and the side wall of the case and insulated and bonded between the case and the cap plate
Data Source
AI summary
A button cell includes an electrode assembly including a first electrode, a second electrode, and a separator between the first electrode and the second electrode; a case connected to the first electrode, housing the electrode assembly, and including an opening exposing the electrode assembly and a side wall defining the opening; a cap plate connected to the second electrode, insulated from and bonded to the side wall of the case, and covering the opening; and a bonding layer located between the cap plate and the side wall of the case, and insulating and bonding the case and the cap plate.