1. Sequential Fe Reduction, Involving Two Different Fe+ Intermediates, in the Conversion Reaction of Prussian Blue in Lithium-Ion Batteries
- Author
-
Química inorgánica, Kimika ez-organikoa, Piernas Muñoz, María José, Castillo Martínez, Elisabeth, Goikolea Núñez, Eider, Blanco Rodríguez, Pablo, Legarra Sáez, Estíbaliz, Saiz Garitaonandia, José Javier, Kim, Soojeong, Fister, Timothy T., Johnson, Christopher S., Rojo Aparicio, Teófilo, Química inorgánica, Kimika ez-organikoa, Piernas Muñoz, María José, Castillo Martínez, Elisabeth, Goikolea Núñez, Eider, Blanco Rodríguez, Pablo, Legarra Sáez, Estíbaliz, Saiz Garitaonandia, José Javier, Kim, Soojeong, Fister, Timothy T., Johnson, Christopher S., and Rojo Aparicio, Teófilo
- Abstract
Ex situ X-ray absorption spectroscopy and in operando 57Fe-Mössbauer spectroscopy measurements are conducted to examine in detail the ongoing reaction mechanism of potassium Prussian blue (K-PB) within the narrow [1.6–0.005 V] voltage range, and so to determine whether this material truly undergoes a conversion reaction, as we proposed elsewhere. The generation of Fe0 is confirmed by both techniques, finding that 40 to 58% of iron gets reduced to metallic iron at 5 mV. The elucidation of the mechanism by in situ 57Fe-Mössbauer spectroscopy further reveals a sequential process for the reduction (lithiation) of the two different iron species initially present in Prussian blue. Both high-spin Fe2+–N first and low-spin FeII–C next go through the unusual Fe1+/I formal oxidation state during the reduction process, before forming surface Fe0 nanoparticles (NPs) below 0.48 V. Upon charge, Fe0 NPs preferentially oxidizes into Fe+–N. Interestingly, these surprising Fe+ species play an important role in decreasing the overpotential during the charge (delithiation) process with respect to other conversion systems.
- Published
- 2022