Fundamental Aspects of Large-Scale Energy Storage System Safety

Abstract

As the scale of energy storage systems increases, safety considerations grow commensurately with the amount of stored energy. The authors summarize a recent review of safety and reliability findings for battery storage and identify R&D gaps, particularly as batteries are scaled into system level hardware. While there have been a number of studies addressing failure of rechargeable batteries in portable computing and consumer electronics, with a small number of studies on electric vehicle battery systems, in the case of stationary batteries for grid energy storage, very little information exists on the fundamental aspects of safety. The aim of this review is to focus on the R&D needs that will allow the community to build on prior knowledge to address issues of abuse and safety for larger, grid scale energy storage systems. The primary focus of the review will be on the underlying materials science, electrochemical processes, and thermal kinetics that can lead to major safety events. Importantly, consideration will be given to identifying cell and system level interactions, how such interactions manifest into catastrophic failures, and the need to develop mitigation strategies. To date, the safety of energy storage systems has been looked at almost exclusively through the narrow lens of cell level failures. While a greater understanding of cell level failures has been critical to the success of rechargeable batteries in consumer electronics, the complexity associated with the scale of energy in grid energy storage applications necessitates consideration of a wider range of system level issues related to power electronics, to power conditioning systems and to fire suppression of large energy storage systems and the surrounding physical infrastructure. Furthermore, the kinetic behavior of cell-level failure must take into account the probability of propagation and thermal runaway that is not indicated in smaller batteries of the same chemistry. We will first provide a summary on the status of current research and outline the immediate and longer term R&D needs to advance the fundamental safety and reliability needs of the grid energy storage industry.