ThermoArc Facilitates Low-Cost Li-Ion Battery Testing

For years, NASA and the battery industry have been improving passive propagation resistant (PPR) Li-ion battery cell technology by enhancing their material and design choices. These efforts help ensure that a single cell’s TR event does not overheat adjacent cells or the entire battery pack ultimately causing fire or explosion. To improve cell integrity, single cells within battery packs are triggered into TR so that the battery pack can be analyzed for its TR resistance. ThermoArc operates by initiating a plasma arc, capable of delivering thermal energy up to 100W, to a very small (1mm diameter) section of the cell. The extremely localized high heat flux rapidly degrades a small section of the internal cell separator, resulting in a short circuit that leads to TR. This technology comprises several components: a high-turn-ratio step-up transformer capable of producing a minimum of 1,000 V upon the secondary winding, an H-bridge electronic circuit to drive the transformer on the primary side, two tungsten electrodes to deliver the plasma arc, and a power supply unit. ThermoArc applications may exist in any Li-ion battery cell/pack testing application where TR must be induced in an individual cell. Such applications could include testing of PPR battery packs to ensure single cell runaway does not cause catastrophic damage, more general battery destructive testing designed to better understand battery failure states, or other experimental testing. Companies interested in licensing this innovation may include those that manufacture internal short-circuit (ISC) cells or other devices used to induce TR at the individual cell level, battery testing firms, and Li-ion battery manufacturers with a focus on Li-ion battery packs for critical applications. ThermoArc is at a technology readiness level (TRL) 5 (component and/or breadboard validation in laboratory environment) and is now available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale. Innovators at NASA Johnson Space Center have developed a battery testing technology called ThermoArc that uses a plasma arc to drive a Li-ion battery cell into thermal runaway (TR) by inducing a localized short circuit. The short circuit is created when the plasma arc breaches the cell and melts a small section of the internal separator causing the anode and cathode to come into contact. This "short" yields rapid heat generation that, if not contained, can potentially cause a fire or explosion. This situation becomes especially dangerous if a single cell’s TR event propagates to other cells within a battery pack, such as those used commercially in aerospace and electric vehicles. Therefore, various testing methodologies have been adopted by battery manufacturers to study TR and the results, and thereby improve TR containment. ThermoArc presents a method that uses a plasma arc to deliver thermal energy to heat up only a small area of a Li-ion battery cell to trigger a TR event. This method ensures that the total heat applied is minimal and does not affect the cell’s thermal properties nor does it make significant electrical or mechanical alterations to the cell. Additionally, ThermoArc technology can be implemented to initiate hundreds of repeatable Li-ion battery cell TR tests significantly cheaper than other TR testing method-ologies given that the only consumables are inexpensive electrodes.