(Invited) Impacts of Environmental Stress Factors on Li-Ion Battery Safety Margins

Abstract

Since the mid-1990’s, many commercial, automotive, and aerospace platforms have transitioned from heritage aqueous electrolyte nickel-based energy storage batteries to lithium-ion battery (LIB) based electrical power subsystems. For space applications, the transition from nickel-hydrogen (Ni-H2) batteries to LIB’s was accelerated by growing concerns with Ni-H2 raw materials obsolescence issues. Although significant research efforts were undertaken to mitigate the risk of Ni-H2 raw materials obsolescence, the recurring cost of maintaining multiple Ni-H2 battery technology supply sources was prohibitive versus the longer-term benefits of supporting a deliberate transition to LIB technologies. Other transitional market forces such as consumer demands to reduce system mass, volume and cost continue to drive the commercial electronics and automotive industries. While it is widely recognized that the mass market for LIB’s in consumer electronics is reaching maturity, the automotive and aerospace marketplace continues to experience new technology growth opportunities. These emerging markets are highly leveraged against economic incentives to pursue safe and reliable LIB design solutions to meet demanding customer requirements. Traditionally, implementing safe and reliable LIB design solutions into aerospace platforms included considerations of simplistic first-order interactions between thermal, mechanical, and electrical environmental stress factors. However, industry experience indicates that the effect of certain synergistic stress factors on LIB performance characteristics in their service environments is a complex multi-dimensional problem. For example, induced and natural environmental stress factors such as thermal cycling, vibration, and radiation have been shown to impact LIB battery performance and in some cases, safety margins. Specifically, certain high-performance LIB aerospace and automotive power systems have recently been challenged to understand the principles governing lithium-ion cell thermal runaway in far greater detail than previously accepted. The severity of lithium-ion cell thermal runaway has created a need for identifying LIB design modifications which reduce degree of severity. The consequences of thermal runaway have the potential to make lithium-ion chemistry an at-risk technology for some applications. To mitigate these risks, investigators from academia, government, and industry have shifted research efforts toward identifying key factors which contribute to the severity of thermal runaway. This work focuses on identifying gaps and opportunities in achieving new paradigms for mitigating LIB safety hazards. Challenges with current technologies to increase LIB safety margins and steps required to reach the readiness level required for successful insertion in an industrial application will also be presented.