(Invited) Life-Cycle Comparison of EV Li-Ion Battery Chemistries Under Grid Duty Cycles

Sunday, 1 October 2017: 16:10
Chesapeake J (Gaylord National Resort and Convention Center)
V. Sprenkle, D. Choi, A. Crawford, and V. Viswanathan (Pacific Northwest National Laboratory)
Energy storage is an integral component to ensure the resiliency and efficiency of a future power grid that is adopting a wider array of distributed generation assets and changing customer usage and expectations. Energy storage can provide a vast array of services, such as back-up power, energy management, voltage support, and frequency regulation, that are critical for grid stabilization. Currently, 77% of the electrochemical energy storage systems in operation in U.S utilize Li-ion batteries developed for commercial and EV applications. To date, the highest value market for energy storage has been frequency regulation services. Potentially, the battery packs in EV could also be used to provide these services also when they are connected to a charging station, however, few studies have addressed the potential impact of providing grid services on the estimated lifetime of the EV battery pack. In this study two leading Li-ion battery chemistries: (NCA) LiNi0.8Co 0.15Al0.05O2 and (LFP) LiFePO4 were obtained from leading manufactures and were subjected to different usage scenarios involving frequency regulation and peak shaving duty cycles with and without the baseline electric vehicle duty cycle. In general, the LFP cells show less aging, higher round trip efficiency and better cycling than NCA when operated under both high and low power applications. For high power applications like frequency regulation, NCA cells are slightly better/comparable to LFP, however the NCA cells show greater degradation and self-discharge during rest.