Enhancing Li-Ion Battery Safety

Integrating Pressure Relief and Breather Devices for Overpressure Mitigation for battery safety.

Author: OsecoElfab

The rapid growth of Li-Ion batteries in various industries, including electric vehicles, portable electronics, and renewable energy storage has thrown a spotlight onto a critical battery safety concern: thermal runaway and its potential to trigger overpressure explosions.

Managing Thermal Runaway

To properly manage thermal runaway, it is essential to put certain safety measures in place. These include preventative measures to reduce risk, such as installing an efficient cooling system or using flame-retardant additives in the electrolyte. There are also further measures aimed at stopping or limiting damage from thermal runaway. These include separator shutdown methods and pressure relief mechanisms such as explosion panels, rupture discs or valves.

The Regulatory Landscape: Commercial vs. Military Vehicles

While there is not any current legislation mandating specific pressure relief solutions for battery packs in commercial and commuter vehicles, military vehicles are bound by the rigorous standards of MIL-PRF-32565. This stringent regulation enforces the inclusion and testing of pressure relief mechanisms to safeguard against overpressure scenarios. This highlights the imperative of such measures for overall safety. Many battery packs seen in the market today offer a plastic breathing type vent as a solution, although metal discs may be used where a more robust solution is required.

Pressure Equalization vs. Pressure Relief

Pressure equalization, commonly referred to as “breathing,” aims to maintain pressure balance within a battery enclosure due to environmental or elevation changes. Think of a plastic gas can in the garage, which may expand in the hot summer months and contract again in the winter. However, pressure equalization alone does not mitigate overpressure risks. In an emergency, excess heat and pressure may need to be relieved very quickly. Rupture discs open in milliseconds at predetermined thresholds to provide active pressure relief and prevent catastrophic explosions.
Some newer products actually combine the breathing function with rapid overpressure relief capability. These space-saving products simplify battery design, as they eliminate the need for an additional component. Breathing and outgassing can be funneled though a single location, meaning there is one less feature to machine or cast on the battery enclosure, where space is very limited. This also makes assembly and forward integration easier.

Dual Devices

Manufacturers use different techniques for combining the two functions – breathing (pressure equalization) and bursting (pressure relief). The all-plastic solution from Donaldsen, for example, combines a porous ePTFE membrane with a plastic, one-way umbrella valve. The membrane allows gases to move in and out of the battery pack for pressure equalization, but in an emergency, high internal pressure is relieved through the umbrella valve or by bursting the membrane.

Another approach comes from Freudenberg Sealing Technologies. Their DiaVent dual devices pairs a breathable membrane for ongoing pressure equalization with a re-closing, spring-loaded shield valve. During emergency degassing, the heat and pressure are directed out of the valve around the edges of the device.

In contrast to this, OsecoElfab’s Dual-Gard device places the breathable membrane at the edge of the device with a metal rupture disc in the center. This allows for mounting the device to the battery enclosure with minimal protrusion, meeting the requirements of MIL-PRF-32565. Being mostly metal rather than plastic, Dual-Gard is a heavy-duty dual device suited to applications such as grid-scale energy storage and large, industrial vehicles, especially in the aerospace and marine sectors.

OsecoElfab DualGard breather and vent disc

Conclusion for enhancing Li-ion battery safety

The absence of legislated mandates for commercial vehicles combined with the rise in popularity of electric solutions underscores the need for proactive safety measures. Integrating rupture discs and dual devices into Li-Ion batteries marks a pivotal stride in enhancing battery safety. Features such as low-profile designs, rapid opening times, holder-less configurations, and all-metal construction are advancing current battery designs. By considering rupture discs and dual devices as an integral part of battery design, manufacturers are underscoring their commitment to making Li-Ion batteries safer, more sustainable and increasingly viable as a future-proof technological solution.

OsecoElfab is a leading global provider of pressure relief solutions, headquartered in the USA and UK. Our purpose is ‘Protecting life. Solutions for a safer, cleaner world.’ Following this purpose, we manufacture rupture discs, explosion vents and burst detection systems to protect people, plant and the environment.

Our innovative solutions for lithium-ion battery protection include rugged, space-saving, and ultra-low-profile designs, as well as dual-function breather-and-rupture disc devices. For the energy storage market we offer specialist explosion panels designed to withstand harsh and outdoor environmental conditions. Our customer-focused services include highly specialized engineering and design consultation, product training seminars, site surveys and a stock consolidation program.

Our two manufacturing facilities in the USA and UK are supported by six regional sales offices and over sixty approved representatives worldwide. Alongside the battery and energy storage markets, our key sectors include chemical processing, pharmaceutical and biopharmaceutical manufacturing, electricity transmission and distribution, powder and bulk handling, gas generation and handling, cryogenics, medical, and aerospace. OsecoElfab is part of the Halma Group, a FTSE 100 company with over 50 subsidiaries worldwide.


Rupture Disc Integration for Overpressure Mitigation

Sizing rupture discs for Li-Ion battery packs presents unique challenges due to varying battery chemistries, sizes, and configurations. Unlike conventional applications, there isn’t a one-size-fits-all formula for rupture disc sizing in battery systems. To ensure the relief area of a rupture disc is sufficient for the battery enclosure and cell configuration, thorough testing is essential. Prototyping and testing different rupture disc sizes and configurations under simulated thermal runaway conditions can provide valuable insights into the ideal rupture disc design for a specific battery pack. The utilization of multiple rupture discs strategically positioned within a battery pack can enhance safety redundancy and optimize pressure relief effectiveness.

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