Joshua Lamb

Propagation testing multi-cell batteries.

Propagation of single point or single cell failures in multi-cell batteries is a significant concern as batteries increase in scale for a variety of civilian and military applications. This report describes the procedure for testing failure propagation along with some representative test results to highlight the potential outcomes for different battery types and designs.

Quantification of Lithium-ion Cell Thermal Runaway Energetics

Much of what is known about lithium-ion cell thermal runaway energetics has been measured and extrapolated from data acquired on relatively small cells (< 3 Ah). This work is aimed at understanding the effects of cell size on thermal runaway energetics on cells from 3 to 50 Ah of both LiFePO4 (LFP) and LiNi0.80Co0.15Al0.05O2 (NCA) chemistries. Results show that for both LFP and NCA cells, the normalized heating rate (W/Ah) increases roughly linearly for cells from 3-38 Ah while the normalized total heat released (kJ/Ah) is relatively constant over that cell size range. The magnitude of the normalized heating rate is on the order of 2x greater for NCA relative to LFP chemistries for 2-3 Ah cells, while that difference is on the order of 10x for 30-40 Ah cells. The total normalized heat release is ~ 15-20% greater for NCA relative to LFP cells across the entire size range studied 3-38 Ah.

Potential Use of Battery Packs from NCAP Tested Vehicles

Several large electric vehicle batteries available to the National Highway Traffic Safety Administration are candidates for use in future safety testing programs. The batteries, from vehicles subjected to NCAP crashworthiness testing, are considered potentially damaged due to the nature of testing their associated vehicles have been subjected to. Criteria for safe shipping to Sandia is discussed, as well as condition the batteries must be in to perform testing work. Also discussed are potential tests that could be performed under a variety of conditions. The ultimate value of potential testing performed on these cells will rest on the level of access available to the battery pack, i.e. external access only, access to the on board monitoring system/CAN port or internal electrical access to the battery. Greater access to the battery than external visual and temperature monitoring would likely require input from the battery manufacturer.

Effect of Gaseous Impurities on Long-Term Thermal Cycling and Aging Properties of Complex Hydrides for Hydrogen Storage

Hydrogen is one of the alternate fuels for vehicular applications where the exhaust is mainly water vapor when used with either fuel cells or internal combustion engines. In the transportation sector, a proton exchange membrane (PEM) fuel cell, that electrochemically combines inputs of pure hydrogen and oxygen (from air), may be used to directly generate electricity for an electric motor drive with water vapor and heat produced as byproducts. However, hydrogen fuel cell technologies must be competitive in this venue with the ubiquitous internal combustion engine using gasoline and diesel fuels, both of which offer an established production and distribution infrastructure as well as a familiar and commonly accepted form of high density and stable energy storage. The United States Department of Energy (DOE) is addressing the standards that a hydrogen fuel system would have to meet as part of their FreedomCAR initiative. Conventionally, hydrogen is compressed in high pressure cylinders with obvious safety issues. The authors believe that hydrogen may be stored in metal hydrides at low pressures. Hydrides may be classified as (a) classical hydrides (heavy hydrides with low wt.%H), and (b) complex hydrides (light weight hydrides with high H-wt.%). In this study, the focus was on practical aspects of complex hydrides related to refilling hydrogen in vehicles at hydrogen gas stations, where one expects ppm levels of impurities. These gaseous impurities affect the performance of the complex hydrides as a medium for storing hydrogen. The main focus of the project was to understand the effect of trace element gases, mixed with hydrogen, on the long-term cycling and aging properties of complex hydrides of Li3N-H2. Another secondary aspect was to test complex hydrides developed by MHCoE partners. In addition, they also conducted thermodynamic and crystallographic research of these hydrides to understand the reaction pathways.