Secondary Battery Bottom Safety Device for Overpressure Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional secondary batteries lack effective safety devices to prevent explosions and fires due to internal pressure increases, and existing solutions like PTCs and CID devices have limitations such as temperature-related issues, restricted application in high-rate discharge, and potential electrolyte leakage.
Innovation Solution
A secondary battery design with a safety device mounted between the electrode core and the bottom of the casing, featuring a conductive current interrupting member and an insulation holding member, which supports the current interrupting member and is welded to the casing, allowing for pressure-induced current interruption without damaging the sealing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PTC thermosensitive element is used as a safety device, then the battery can be protected from overheating, but the battery cannot work normally during high-rate discharge due to temperature rise
Solution Approach 1:
The safety device is segmented into distinct functional components: a current interrupting member for electrical isolation and a holding member for mechanical support. This segmentation allows the current interrupting member to respond to pressure without being influenced by temperature-induced resistance changes, enabling both safety protection and high-rate discharge capability.
Solution Approach 2:
The patent replaces the thermal-based PTC mechanism with a pressure-based mechanical mechanism. The current interrupting member is designed to break or detach when subjected to excessive internal pressure, directly responding to the root cause of battery failure (pressure buildup) rather than temperature, thus avoiding the limitation of PTC devices during high-rate discharge.
2Reliability
If a CID device is mounted at the anode end, then the battery can be protected from overpressure, but the sealing process is restricted and internal pressure remains high
Solution Approach 1:
Instead of mounting the safety device at the traditional anode end (open end), the patent inverts the approach by mounting the safety device at the bottom end of the battery. This inversion allows the battery to be sealed first and then have the safety device installed, eliminating the restriction on sealing processes and reducing internal pressure while maintaining overpressure protection.
Solution Approach 2:
The battery sealing process is performed before installing the safety device. This preliminary action of sealing allows the use of various sealing methods (laser welding, pressing sealing, etc.) without restriction, and the safety device is subsequently installed through the bottom opening, avoiding the high internal pressure problem associated with post-sealing CID installation.
3Reliability
If a groove is engraved or pressed on the battery surface as a weak portion, then the battery can be protected when internal pressure rises, but it is difficult to machine the groove and ensure uniform thickness
Solution Approach 1:
The patent extracts the safety function from the battery casing surface (where grooves would be difficult to machine with uniform thickness) and places it in a dedicated safety device mounted at the bottom. This extraction allows the use of standard manufacturing processes for both the battery casing and the safety device, avoiding the difficulty of machining precise grooves while maintaining overpressure protection.
4Ease of manufacture
If pressing sealing process is used to seal the battery with CID device, then the battery can be sealed, but electrolyte leakage occurs leading to environment pollution and shorter service life
Solution Approach 1:
By inverting the sequence and method of sealing, the patent allows the use of laser welding or other advanced sealing methods that provide better sealing performance compared to traditional pressing sealing. The safety device is installed after sealing, enabling the use of more effective sealing processes that prevent electrolyte leakage while maintaining ease of manufacture.
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 design effectively prevents safety accidents by interrupting current flow when internal pressure exceeds a threshold, allowing for flexible battery formation processes and sealing methods, reducing the risk of electrolyte leakage and enhancing safety without compromising performance.
Implementation Method 1
The assembly welding portion of the current interrupting member of the safety device is welded to the inner surface of the bottom of the casing
Implementation Method 2
When the internal pressure of the battery rises, the main body of the current interrupting member is under a tension force. Once the tension force exceeds a certain degree, the main body of the current interrupting member is broken, or the welding structure between the assembly welding portion of the current interrupting member and the bottom of the casing is damaged
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A secondary battery provided with a safety element (16) comprising a conductive current interrupter (161) and an insulation holder (162) at thereof bottom. By safety element provided at the bottom of the battery, either sealed formation technology or open-formation technology is allowed in battery formation processing, and any other sealing method is selectable as well as pressing sealing.