a Lithium-ion batteries are being used in increasingly demanding applications where safety and reliability are of utmost importance. Thermal runaway presents the greatest safety hazard, and needs to be fully understood in order to progress towards safer cell and battery designs. Here, we demonstrate the application of an internal short circuiting device for controlled, on-demand, initiation of thermal runaway. Through its use, the location and timing of thermal runaway initiation is pre-determined, allowing analysis of the nucleation and propagation of failure within 18 650 cells through the use of high-speed X-ray imaging at 2000 frames per second. The cause of unfavourable occurrences such as sidewall rupture, cell bursting, and cell-to-cell propagation within modules is elucidated, and steps towards improved safety of 18 650 cells and batteries are discussed. Broader contextFrom portable electronics to grid-scale storage, high energy density Li-ion batteries are ubiquitous in today's society. Such cells can and do fail, sometimes catastrophically, releasing large amounts of energy. To facilitate safer and more reliable cell designs, the importance of understanding failure mechanisms of Li-ion cells is widely recognised. Here, we demonstrate the application of a novel device that is capable of generating an internal short circuit within commercial cell designs, on-demand, and at a predetermined location. This enables us to test more effectively the ability of safety devices of cells and modules to withstand 'worst-case' failure scenarios. By combining the use of this device with high-speed X-ray imaging at 2000 frames per second, we characterise for the first time the initiation and propagation of thermal runaway from a known location within a Li-ion cell. The insights achieved in this study are expected to guide the design and development of safer and more reliable Li-ion cells.

Electric vehicles (EVs) are experiencing a rise in popularity over the past few years as the technology has matured and costs have declined, and support for clean transportation has promoted awareness, increased charging opportunities, and facilitated EV adoption. Suitably, a vast body of literature has been produced exploring various facets of EVs and their role in transportation and energy systems. This paper provides a timely and comprehensive review of scientific studies looking at various aspects of EVs, including: (a) an overview of the status of the light-duty-EV market and current projections for future adoption; (b) insights on market opportunities beyond light-duty EVs; (c) a review of cost and performance evolution for batteries, power electronics, and electric machines that are key components of EV success; (d) charging-infrastructure status with a focus on modeling and studies that are used to project charging-infrastructure requirements and the economics of public charging; (e) an overview of the impact of EV charging on power systems at multiple scales, ranging from bulk power systems to distribution networks; (f) insights into life-cycle cost and emissions studies focusing on EVs; and (g) future expectations and synergies between EVs and other emerging trends and technologies. The goal of this paper is to provide readers with a snapshot of the current state of the art and help navigate this vast literature by comparing studies critically and comprehensively and synthesizing general insights. This detailed review paints a positive picture for the future of EVs for on-road transportation, and the authors remain hopeful that remaining technology, regulatory, societal, behavioral, and business-model barriers can be addressed over time to support a transition toward cleaner, more efficient, and affordable transportation solutions for all.

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Battery management is essential for achieving desired performance and life cycle from a particular battery pack in Electric and Hybrid Vehicles (EV and HEV). The batteries must be thermally managed in addition to the electrical control. In order to design battery pack management systems, the designers need to know the thermal characteristics of modules and batteries. Thermal characteristics that are needed include heat capacity of modules, temperature distribution and heat generation from modules under various charge/discharge profiles. In the last few years, we have been investigating thermal management of batteries and conducting tests to obtain thermal characteristics of various EV and HEV batteries. We used a calorimeter to measure heat capacity and heat generation from batteries and infrared equipment to obtain thermal images of battery modules under load. In this paper, we will present our approach for thermal characterization of batteries (heat generation, heat capacity, and thermal images) by providing selected data on valve regulated lead acid, lithium ion, and nickel zinc battery moduledcells. For each battery type, the heat generation rate depends on the initial state of charge, initial temperature, and charge/discharge profile. Thermal imaging indicated that the temperature distribution in modules/cells depends on their design.

NREL, in conjunction with NASA, has developed an internal short circuit (ISC) device that can be placed anywhere within the battery and may be used with both spirally wound and flat-plate cells.  The internal short device is small compared to other shorting techniques being developed by industry and does not rely on mechanical pressure deforming the battery to activate the short as do most of the other “internal shorts” being developed.  The battery can be used and cycled within normal operating conditions without activating the internal short device.  This allows for the battery to be aged prior to activation of the internal short.  Another unique feature of NREL’s internal short device is that the resistance of the short can be tuned to simulate a hard (more energetic) or soft (less energetic) short. Once the short is activated, the positive and negative components of the battery are internally connected within the cell and internal short circuit begins.  NREL’s ISC can simulate all four types of shorts within a cell – collector to collector, collector to anode, collector to cathode and collector to collector. NREL uses the internal short circuit device to better understand the failure modes of Li-ion cells and to validate NREL’s abuse models.  The internal short produced by NREL’s device is consistent and is being developed as an analysis tool for battery manufacturers and other national laboratories as well as OEMs. This has broad-reaching applications as automakers bring electrified vehicles to market in larger Over the past three years, NREL has implanted their ISC into cylindrical 18650 LiCoO2 cells to determine the effectiveness of a shutdown separator with regards to ISC type – in particular, we compared a collector to collector ISC versus a collector to aluminum ISC.  NREL has also been using the ISC to determine the effectiveness of a non-flammable electrolyte in LiMnO4 pouch cells.  During our presentation, we will update the battery community on the effectiveness of the ISC in understanding the behavior of these safety devices incorporated into these two cell types and chemistries.  We will also show how the ISC can be used for propogation testing in modules and packs.