LLIBTA Symposium - Large Lithium Ion Battery Technology and Application
Track B: Battery Engineering and Application
Tuesday, February 5 to Wednesday, February 6, 2013
AABC 2013 LLIBTA Symposium - Large Lithium Ion Battery Technology and Application - Track B: Battery Engineering and Application - session B3
Battery Safety and Abuse Tolerance Validation
Safety of the early Large Li-Ion battery installations will have the greatest impact on the market acceptance of the technology in automotive and stationary applications. In this session, we will discuss safety-enhancing technology and the validation of battery safety under ordinary and abusive conditions.
Dr. Brian M. Barnett, Vice President, TIAX LLC
Dr. Brian Barnett is a Vice President at TIAX LLC where his multidisciplinary team develops advanced battery materials, battery technologies, and battery-safety technologies. He has played a founding role in developing polymer electrolyte battery technology, carbon anode materials, battery safety technologies, and high-energy, high-power cathode material. Prior to TIAX, Dr. Barnett was a Vice President and Member of the Board of Directors at Arthur D. Little where he directed battery activities.
New Approaches to Safety for Automotive Lithium-Ion Batteries
Dr. Brian Barnett, Vice President, TIAX LLC
Safety of lithium-ion batteries is a critical topic that has not received adequate attention in the past, largely due to the fact that data regarding safety failures have been severely restricted. As a result, there are numerous misunderstandings regarding battery safety and safety testing. Safety failures of lithium-ion cells can result from a variety of triggers; examples of which include overheating, overcharging, crushing, mechanical impact, external shorting and development of internal shorts. The underlying physics for these different failure mechanisms can be quite different, with different reaction kinetics and timing to failure post trigger. Most Li-ion safety failures that occur in the field take place due to the slow and rare development of internal short circuits that mature to the point that they result in thermal runaway. An adequate safety test for internal short development, that replicates the conditions by which such failures occur, is not available.
It turns out that many of the safety tests carried out in the laboratory or factory do not replicate the conditions by which safety incidents occur in the field or the range of possible triggers. Of concern, sometimes these tests are far too severe, sometimes not adequate and sometimes they produce stochastic, inconsistent results.
In this presentation, safety events and mechanisms, as well as associated safety testing considered to represent with various triggers, will be characterized with reference to a combination of experimental measurements, FEA modeling/simulations, thermal calculations and movie clips of important test results. The work provides insights regarding the initiation and progression to thermal runaway of battery safety incidents, but also elucidates critical issues pertaining to the relevance of safety testing. In a surprising number of cases, the insights contrast with how the battery community typically tests for safety, evaluates and selects battery materials, identifies causes of safety incidents and considers options for development of new safety technologies.
The presentation will offer a specific framework for use in thinking about appropriate safety testing that is better aligned with potential triggers and will also describe new safety detection technology, suitable for integration in a BMS, that warns of incipient internal short development.
Approaches to Evaluating and Improving Lithium-Ion Battery Safety
Dr. Chris Orendorff, Battery Abuse Testing Laboratory Team Lead, Sandia National Laboratory
As lithium-ion battery technologies mature, the size and energy of these systems continues to increase for emerging applications in transportation, grid storage, military use and aerospace. In fact, broadening the application space for lithium-ion batteries from the consumer electronics industries to these emerging markets increases their size from 1-50 Wh batteries for smart phones and laptops to >50 kWh for electric vehicles (EVs) and MWh scale for utility storage systems. As these energy storage systems grow, safety and reliability issues will become increasingly important. Moreover, as the application space changes for these energy storage devices, the failure modes and mitigations for hazards associated with these failures will also change and evolve. While system or use controls are often designed into large batteries to mitigate more predictable problem scenarios (overcharge, cell imbalance, high voltage short circuit, etc.), it is a significant challenge to design for unpredictable field failure safety incidents (internal short, failure propagation, etc.). Moreover, there are fundamental materials chemistry improvements that can be made in order to improve the overall inherent safety of a large battery (and therefore, the system), without the need for relying solely on ancillary external system control electronics.
This presentation highlights our work to better understand safety issues and abuse response of large-scale lithium-ion battery systems and development efforts to improve inherent lithium-ion battery safety.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
Customer Expectations & Engineering of Safety in xEVs
Galen Ressler, Technical Fellow, General Motors
Customers expect that clean electric vehicle transportation poses no greater risk to their personal safety than any other vehicles on the road today. In fact, media focus on early field events has heightened the concern that battery powered xEVs could pose safety concerns. Furthermore, industry activity has accelerated to develop safety standards of performance for xEVs and the batteries that are used in them.
GM and other mainstream OEMS employ a layered safety process that has been discussed in this forum in prior years. This presentation will survey some specific considerations for product design, analysis, & verification of battery energy storage systems and the vehicles they are contained within that demonstrate the challenges and considerations of fielding safe xEV products. The developing industry efforts will continue to raise the bar on what is needed at a minimum to insure necessary safety performance. Additional “due care” verification may be needed in other areas to insure customer confidence in xEV products as large scale electrification proceeds
Some relevant safety related topics of interest that will be discussed include:
- Appropriate handling, including depowering, of battery packs that are rendered inoperable in crashed or other damaged
- Analyzing battery pack crash forces in xEVs in order to determine crash characteristics and how it relates to proposed industry battery standards.
- Considerations for liquid cooled batteries vs. air cooled batteries in terms of safety performance and failure modes including liquid compatibility inside battery packs.
- High voltage safety considerations including considerations for high voltage conductor spacing and interpretation of industry requirements in product designs.
- Discussion on likelihood of cell short circuit behavior including potential thermal runaway based on industry and test experience and high severity outcome affects including propagation beyond single cell failures.
Finally, challenges for future battery safety related technical development will be outlined.
BYD’s Approach to Battery Safety for Automotive Applications
Micheal Austin, Vice President, BYD Company Ltd.
According to the U.S. Fire Administration’s TOPICAL FIRE RESEARCH SERIES, July 2001 “one in every four fire department responses is to a vehicle fire” (referring to internal combustion vehicles catching fire), yet US and the world wide media seems to focus on any and every electric vehicle fire with very high scrutiny.
BYD boasts to have not only the most environmentally-friendly battery chemistry used in EV’s but also one of the safest. This boast was put to the test on the morning of May 26th, 2012, when a BYD all-electric taxi was rear-ended at very high speed, was thrown into a large tree and subsequently caught on fire, exposing the batteries to extreme thermal conditions.
BYD will discuss the accident findings from the Shenzhen Academy of Metrology and Quality Inspection (SAMQI) who chartered a team of 13 authoritative experts from China’s leading investigative bodies;
- China Automotive Technology and Research Center,
- Research Institute of Highway Ministry of Transport,
- Tianjin Fire Research Institute,
- Fire Brigade of Guangdong Province
- North Vehicle Research Institute
- Shenzhen Academy of Metrology and Quality Inspection
Besides the collision results, BYD will describe why BYD’s iron-phosphate battery technology is more stable, even “fire safe”, meaning that it does not explode like other batteries in direct flames and it does not produce oxygen when the battery chemistry is decomposing (at extremely high temperatures producing a catalyst for the fire) like other Lithium-Ion batteries. Therefore, the risk of uncontrolled combustion, sometimes called “thermal runaway”, can be avoided.
NHTSA’s Role and Perspective on Lithium-Ion Battery Safety
Phil Gorney, Safety Research Engineer, National Highway Traffic Safety Administration