Cell Vent Retention Structure to Prevent Coil Ejection
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Solution Overview
Problem
Cylindrical electrochemical lithium cells, such as 18650 and 21700, can experience coil expulsion during thermal runaway, leading to safety risks due to the mechanical weakness of the positive pole vent, which can cause the coil to be ejected and ignite neighboring cells.
Innovation Solution
A safety device with a holding device to retain the coil within the cell and a gas releasing mechanism to allow controlled gas expulsion, featuring a frame, abutment pads, and a perforable film to manage pressure and prevent coil expulsion, while ensuring gas release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a rupture disk is used as an overpressure vent, then gases can be released to prevent explosion, but the mechanical weakness of the positive pole vent can cause the coil to be expelled from the cell
Solution Approach 1:
A holding device acts as an intermediary between the rupture disk and the coil, providing mechanical support to the positive pole and preventing coil expulsion while allowing gas to pass through the rupture disk. The holding device includes a frame fixed to the container and holding means that abut the positive pole, distributing the mechanical stress and preventing structural failure during thermal runaway.
Solution Approach 2:
The holding device is pre-installed in the cell before thermal runaway occurs, providing structural reinforcement to the positive pole in advance. This beforehand cushioning ensures that when the rupture disk breaks under overpressure, the positive pole has sufficient mechanical strength to contain the coil while still allowing gas release.
2Strength
If the positive pole vent is made mechanically stronger to prevent coil expulsion, then coil retention is improved, but gas release capability may be compromised
Solution Approach 1:
The positive pole structure is segmented into multiple functional components: the original vent structure for gas release and the added holding device with frame and holding means for structural reinforcement. This segmentation allows each component to perform its specific function - the vent structure maintains gas release capability while the holding device provides the necessary mechanical strength to prevent coil expulsion.
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
The solution effectively retains the coil inside the cell during thermal runaway, preventing coil expulsion and allowing safe gas release, thereby enhancing safety by reducing the risk of secondary thermal runaway in neighboring cells.
Implementation Method 1
at least one rupture initiator, designed to break in the event of a fault so as to expel the gases
Implementation Method 2
A holding device arranged to ensure an abutment against said second wall of the container so as to hold it in position in the event of thermal runaway and to retain the coil on the inside of said container
Data Source
AI summary
A safety device adapted to an electrochemical cell, the cell having a container in which a coil is placed, the container including at least one first wall provided with at least one rupture initiator, designed to break in the event of a fault so as to expel the gases, and a second wall arranged to ensure the coil is held in said container, the safety device has a holding device arranged to ensure an abutment against said second wall of the cell so as to hold it in position in the event of thermal runaway and to retain the coil on the inside of the container, a gas releasing device, arranged to ensure the expulsion of the gases from the cell, in the event of thermal runaway.