Mechanism Study of Superfast (De)lithiation Process of Conversion Materials

Fast-charging battery materials are needed to solve the bottleneck of long charging times in electric vehicles, which help reduce CO2 emissions. The transportation sector is the largest contributor to CO2 emissions in the U.S. However, most lithium-ion battery cathode materials are not capable of super-fast charging, which is a long-standing challenge for energy storage. This project will use a combination of experiments and computational simulations to improve understanding of metal ion transport in solid particles. Results from the project will help guide the design of next-generation battery materials to realize superfast charging of batteries. These batteries will keep the U.S. on the leading edge of energy and power storage technologies across various sectors from EVs to weapon systems. This project will provide understanding of the super-fast ion-motion mechanism within a solid host and expand knowledge about metal ion motion under extreme conditions. Fast operando XANES, XANES simulations, and molecular orbital analysis will be used to examine the valence state change of Fe in FeOF-G conversion materials and the local bonding structure changes to determine the crystalline structure of intermediates during (de)lithiation (charge/discharge) process. The team will investigate morphology and structure change of FeOF-G (i.e. intermediate species, final products and the distribution of different species) using both TEM and pseudo in situ TEM. The researchers will also employ first-principle modeling to analyze possible superfast charging pathways and determine possible (de)lithiation mechanisms at extremely fast charging rates could enable superfast charging. The investigators will explore the effect of charging rate (i.e. capacitive capacity) on the Faradic capacity and develop a new method of symmetric cell to exclude the anode effect for superfast charging. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.