Atomistic Observation and Transient Reordering of Antisited Li/Fe Defects toward Sustainable LiFePO4

Abstract

The Li/Fe disordering confined within the single unit cells of LiFePO4 (LFP) crystals has been notoriously plaguing their reversible Li+ storage, capacity, and thus service life, posing a grand challenge to sustainable battery technologies. Yet, the atomistic mechanisms of such disordering are scarcely explored, not to mention efficient strategies to reorder the antisited Li/Fe and rejuvenate LFP. Intuitively, the reordering of antisited Li/Fe should occur via Li-Fe inter-atomic "leap" within the Å-scale unit cell, given the kinetic energy barrier being overcome by a transient stimulus. We herein report the high-temperature shock (HTS) technique to trigger such atomic-scale "leaping" movement of antisited Li-Fe pairs: with the high-temperature field being transiently exerted through each bulk LFP crystal, the Li-Fe inter-atomic reordering occurs swiftly and coherently from unit cell to unit cell in milliseconds, far outpacing the onset of potential detrimental side reactions (such as impurity diffusion and LFP phase deterioration). Combining in-depth atom-resolved microscopic imaging, theoretical calculation, and property evaluation, three types of Li/Fe disordering were identified and efficiently repaired on the order of seconds, along with superior electrochemical performances. This work not only discloses the disordering and reordering fundamentals of the LFP system but also proposes an efficient and sustainable strategy to regenerate aged and degraded LFP with advanced performance and significant techno-economic benefits.