(172b) The Versatile VSP2: The New Battery Testing Apparatus

As the world strives to reduce carbon dioxide emissions to “Net Zero by 2050,” there is a rapidly growing demand for not only more batteries, but cheaper and more efficient ones. Batteries will play a pivotal role in the emissions reduction plan by enhancing energy storage, integrating renewable energy sources, and electrifying transportation. Reducing emissions in the transportation sector is especially crucial because it is one of the largest contributors to global emissions. This had led to several policies financially incentivizing the development, manufacturing, and consumer purchase of Electrical Vehicles (EV). Most EV systems today are powered by lithium-ion batteries which are popular because of their high energy density, ability to recharge, and their lightweight among other chemical and physical properties.

While the high energy density of lithium-ion or other chemistry type batteries is a benefit to their many applications, it also poses a significant safety hazard that needs to be addressed. The 2018 Status Report on High Energy Density Batteries Project by the US Consumer Product Safety Commission identified more than 25,000 incidents of overheating or fire hazards with more than 400 types of consumer products between the years of 2012 through halfway of 2017. With the expected large increase in battery manufacturing and employment in a variety of sectors, it is probable that this rate could increase without an improved understanding of the thermal stability of batteries and enhanced safety features of the battery and its auxiliary systems.

There is a seemingly growing number of methodologies for assessing performance and certification testing protocols of battery systems, many of which have a strong emphasis on safety and abuse testing. Some examples of methodologies available include IEC 62660, ISO 12405, ISO 6469, UL 9540, and UL 2580. While a large number of standards are available, generally, the types of tests recommended include runaway testing initiated by different sources such as: thermal, vibration, impact, external short-circuit, overcharge, and forced-discharge, as well as subsequent flammability testing of off-gas products.

The Vent Sizing Package 2 (VSP2) is a low-phi calorimeter used to study runaway chemical reactions by measuring directly saleable temperature and pressure generation rates adiabatically. The VSP2 was designed to be versatile and robust allowing for flexibility in the types of reactions and upset scenarios studied.

This paper discusses the modifications made to the VSP2 system to allow for the study of runaway reactions within battery cells. These extensions allow for the determination of crucial safety parameters such as thermal runaway temperature, adiabatic tracking of thermal runaway, determination of off-gas temperature, quantification of off-gas, and collection of off-gas for additional testing. Descriptions of the test setup and posttest observations and experimental data showing the thermal runaway profile of LG 18650 MJ1 battery cells are provided. Initiation techniques explored in the paper include electrical via external short circuit, mechanical via nail penetration, and thermal via temperature ramp. A discussion on flammability testing of the collected off-gas products is provided with a highlight on potential data applications. The paper concludes with possible next steps to continue to improve the technique and ultimately commercialize the technology.