BATTERY TECHNOLOGY
Making lithium-ion based batteries
SAFER
ADA Technologies’ QiStop materials show promise in mitigating cascading thermal runaway By Kevin B. Roth Heat and flame produced by a cascading thermal runaway failure during a test. CREDIT: ADA TECHNOLOGIES
L
ithium-ion batteries (LIBs) are ubiquitous today, from the single battery cell powering our phones to the thousands of cells powering a Tesla Model S. Such widespread use is due in part to the high energy density inherent to lithium-based systems. For this reason, LIBs power most of today’s electric vehicles (EVs), although the specific chemistries may vary. The mining industry has recently recognized the many advantages of EVs, in particular as it relates to underground mining. Traditionally, underground mining equipment has been diesel-powered. Transitioning such equipment to electric power represents a significant safety improvement to mine workers by avoiding diesel fumes and particulate matter while substantially reducing cost for ventilation equipment and demand associated with underground diesel use. The inclusion of LIBs in mining equipment introduces a new but wellknown safety concern: LIB thermal runaway. Thermal runaway can occur after a cell experiences damage, either externally or internally initiated (often due to manufacturing defects), causing exothermic decomposition of the cell components resulting in an uncontrolled energy release. This energy release can
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MINING JOURNAL
cause cell deflagration (combustion at subsonic speed), during which cell electrolyte can burn uncontrollably, creating extreme heat and fire reaching temperatures as high as 1,000°C. The image above demonstrates how destructive a battery fire can be, even with only a few cells. This risk is amplified when cells are packed tightly together into battery packs, especially on the scale of the thousands of Watt-hours required to power heavy machinery. If a single cell in a pack undergoes a thermal runaway event, the heat and fire generated from that event can easily damage adjacent cells, triggering adjacent cell thermal runaway. In addition, in case of violent deflagration, physical damage to adjacent cells is also common due to projectile debris from the compromised cell. Such a chain of events can result in a “domino-effect” causing cascading failure of the entire battery. While most battery systems have some sort of active or passive cooling mechanism to mitigate battery heating during normal operation, these protection schemes are not designed to mitigate the extreme temperatures associated with thermal runaway events. This issue is well known across all industries and agencies that use LIBs as primary power sources, e.g. EVs, hybrid electric vehicles (HEVs), Department of
Transportation (DOT), Federal Aviation Administration (FAA) and Department of Defense (DOD). In parallel with private sector investments in the EV market, there has also been significant interest and investment from the U.S. federal government for research and development of viable solutions to this thermal runaway problem. ADA Technologies has been at the forefront of solutions and high-performance material development for prevention of cascading thermal runaway in LIBs for the past 10 years, through collaborations with industry, academia and the U.S. government. Examples of some of ADA’s sponsors and collaborators include the U.S. Air Force (USAF), U.S. Navy, FAA, the National Institute for Occupational Safety and Health of the Centers for Disease Control, (CDC/ NIOSH) and two major international LIB manufacturers. More recently, with the increase in EVs for mining applications, the CDC/NIOSH has also recognized the need for more research in the area of thermal runaway, and has funded ADA to study the use of its material solutions in underground mining applications. During these research projects, ADA has developed thin, lightweight materials (under the trademarked family name of QiStop) capable of effectively preventing propagation of www.canadianminingjournal.com
